Awesome

Rambda

Rambda is smaller and faster alternative to the popular functional programming library Ramda. - Documentation

❯ Example use

import { compose, map, filter } from 'rambda'

const result = compose(
  map(x => x * 2),
  filter(x => x > 2)
)([1, 2, 3, 4])
// => [6, 8]

You can test this example in <a href="https://rambda.now.sh?const%20result%20%3D%20R.compose(%0A%20%20R.map(x%20%3D%3E%20x%20*%202)%2C%0A%20%20R.filter(x%20%3D%3E%20x%20%3E%202)%0A)(%5B1%2C%202%2C%203%2C%204%5D)%0A%0A%2F%2F%20%3D%3E%20%5B6%2C%208%5D">Rambda's REPL</a>

• Differences between Rambda and Ramda
• API
• Changelog

❯ Rambda's advantages

TypeScript included

TypeScript definitions are included in the library, in comparison to Ramda, where you need to additionally install @types/ramda.

Still, you need to be aware that functional programming features in TypeScript are in development, which means that using R.compose/R.pipe can be problematic.

Important - Rambda version 7.1.0(or higher) requires TypeScript version 4.3.3(or higher).

Understandable source code due to little usage of internals

Ramda uses a lot of internals, which hides a lot of logic. Reading the full source code of a method can be challenging.

Better VSCode experience

If the project is written in Javascript, then go to source definition action will lead you to actual implementation of the method.

Immutable TS definitions

You can use immutable version of Rambda definitions, which is linted with ESLint functional/prefer-readonly-type plugin.

import {add} from 'rambda/immutable'

Deno support

Latest version of Ramba available for Deno users is 3 years old. This is not the case with Rambda as most of recent releases are available for Deno users.

Also, Rambda provides you with included TS definitions:

// Deno extension(https://marketplace.visualstudio.com/items?itemName=denoland.vscode-deno)
// is installed and initialized
import * as R from "https://deno.land/x/rambda/mod.ts";
import * as Ramda from "https://deno.land/x/ramda/mod.ts";

R.add(1)('foo') // => will trigger warning in VSCode as it should
Ramda.add(1)('foo') // => will not trigger warning in VSCode

Dot notation for R.path, R.paths, R.assocPath and R.lensPath

Standard usage of R.path is R.path(['a', 'b'], {a: {b: 1} }).

In Rambda you have the choice to use dot notation(which is arguably more readable):

R.path('a.b', {a: {b: 1} })

Please note that since path input is turned into array, i.e. if you want R.path(['a','1', 'b'], {a: {'1': {b: 2}}}) to return 2, you will have to pass array path, not string path. If you pass a.1.b, it will turn path input to ['a', 1, 'b']. The other side effect is in R.assocPath and R.dissocPath, where inputs such as ['a', '1', 'b'] will be turned into ['a', 1, 'b'].

Comma notation for R.pick and R.omit

Similar to dot notation, but the separator is comma(,) instead of dot(.).

R.pick('a,b', {a: 1 , b: 2, c: 3} })
// No space allowed between properties

Speed

Rambda is generally more performant than Ramda as the benchmarks can prove that.

Support

One of the main issues with Ramda is the slow process of releasing new versions. This is not the case with Rambda as releases are made on regular basis.

❯ Missing Ramda methods

• construct - Using classes is not very functional programming oriented.
• constructN - same as above
• into - no support for transducer as it is overly complex to implement, understand and read.
• invert - overly complicated and limited use case
• invertObj
• invoker
• keysIn - we shouldn't encourage extending object with .prototype
• lift
• liftN
• mapAccum - Ramda example doesn't looks convincing
• mapAccumRight
• memoizeWith - hard to imagine its usage in context of R.pipe/R.compose
• mergeDeepWith - limited use case
• mergeDeepWithKey
• mergeWithKey
• nAry - hard to argument about and hard to create meaningful TypeScript definitions
• nthArg - limited use case
• o - enough TypeScript issues with R.pipe/R.compose to add more composition methods
• otherwise - naming is confusing
• pair - left-pad types of debacles happens partially because of such methods that should not be hidden, bur rather part of your code base even if they need to exist.
• partialRight - I dislike R.partial, so I don't want to add more methods that are based on it
• pipeWith
• project - naming is confusing, but also limited use case
• promap
• reduceRight - I find right/left methods confusing so I added them only where it makes sense.
• reduceWhile - functions with 4 inputs - I think that even 3 is too much
• reduced
• remove - nice name but it is too generic. Also, Rambdax has such method and there it works very differently
• scan - hard to explain
• sequence
• splitWhenever
• symmetricDifferenceWith
• andThen
• toPairsIn
• transduce - currently is out of focus
• traverse - same as above
• unary
• uncurryN
• unfold - similar to R.scan and I find that it doesn't help with readability
• unionWith - why it has its usage, I want to limit number of methods that accept more than 2 arguments
• until
• useWith - hard to explain
• valuesIn
• xprod - limited use case
• thunkify
• __ - placeholder method allows user to further customize the method call. While, it seems useful initially, the price is too high in terms of complexity for TypeScript definitions. If it is not easy exressable in TypeScript, it is not worth it as Rambda is a TypeScript first library.

The following methods are not going to be added(reason for exclusion is provided as a comment):

❯ Install

• yarn add rambda

• For UMD usage either use ./dist/rambda.umd.js or the following CDN link:

https://unpkg.com/rambda@CURRENT_VERSION/dist/rambda.umd.js

• with deno

import {add} from "https://deno.land/x/rambda/mod.ts";

Differences between Rambda and Ramda

• Rambda's type detects async functions and unresolved Promises. The returned values are 'Async' and 'Promise'.

• Rambda's type handles NaN input, in which case it returns NaN.

• Rambda's forEach can iterate over objects not only arrays.

• Rambda's map, filter, partition when they iterate over objects, they pass property and input object as predicate's argument.

• Rambda's filter returns empty array with bad input(null or undefined), while Ramda throws.

• Ramda's clamp work with strings, while Rambda's method work only with numbers.

• Ramda's indexOf/lastIndexOf work with strings and lists, while Rambda's method work only with lists as iterable input.

• Error handling, when wrong inputs are provided, may not be the same. This difference will be better documented once all brute force tests are completed.

• TypeScript definitions between rambda and @types/ramda may vary.

If you need more Ramda methods in Rambda, you may either submit a PR or check the extended version of Rambda - Rambdax. In case of the former, you may want to consult with Rambda contribution guidelines.

❯ Benchmarks

There are methods which are benchmarked only with Ramda and Rambda(i.e. no Lodash).

Note that some of these methods, are called with and without curring. This is done in order to give more detailed performance feedback.

The benchmarks results are produced from latest versions of Rambda, Lodash(4.17.21) and Ramda(0.30.1).

❯ Used by

• ESLint plugin Mocha

• WatermelonDB

• Walmart Canada reported by w-b-dev

• VSCode Slack integration

• Webpack PostCSS

• MobX-State-Tree decorators

• Rewrite of the Betaflight configurator

• MineFlayer plugin

API

add

It adds a and b.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.add(2%2C%203)%20%2F%2F%20%3D%3E%20%205">Try this <strong>R.add</strong> example in Rambda REPL</a>

addIndex

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.addIndex(R.map)((val%2C%20idx)%20%3D%3E%20val%20%2B%20idx%20%2B%201%2C%20%5B1%2C%202%2C%203%5D)%0A%2F%2F%20%3D%3E%20%5B2%2C%204%2C%206%5D">Try this <strong>R.addIndex</strong> example in Rambda REPL</a>

addIndexRight

Same as R.addIndex, but it will passed indexes are decreasing, instead of increasing.

adjust

adjust<T>(index: number, replaceFn: (x: T) => T, list: T[]): T[]

It replaces index in array list with the result of replaceFn(list[i]).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.adjust(%0A%20%200%2C%0A%20%20a%20%3D%3E%20a%20%2B%201%2C%0A%20%20%5B0%2C%20100%5D%0A)%20%2F%2F%20%3D%3E%20%5B1%2C%20100%5D">Try this <strong>R.adjust</strong> example in Rambda REPL</a>

adjust<T>(index: number, replaceFn: (x: T) => T, list: T[]): T[];
adjust<T>(index: number, replaceFn: (x: T) => T): (list: T[]) => T[];

import { cloneList } from './_internals/cloneList.js'
import { curry } from './curry.js'

function adjustFn(
  index, replaceFn, list
){
  const actualIndex = index < 0 ? list.length + index : index
  if (index >= list.length || actualIndex < 0) return list

  const clone = cloneList(list)
  clone[ actualIndex ] = replaceFn(clone[ actualIndex ])

  return clone
}

export const adjust = curry(adjustFn)

import { add } from './add.js'
import { adjust } from './adjust.js'
import { pipe } from './pipe.js'

const list = [ 0, 1, 2 ]
const expected = [ 0, 11, 2 ]

test('happy', () => {})

test('happy', () => {
  expect(adjust(
    1, add(10), list
  )).toEqual(expected)
})

test('with curring type 1 1 1', () => {
  expect(adjust(1)(add(10))(list)).toEqual(expected)
})

test('with curring type 1 2', () => {
  expect(adjust(1)(add(10), list)).toEqual(expected)
})

test('with curring type 2 1', () => {
  expect(adjust(1, add(10))(list)).toEqual(expected)
})

test('with negative index', () => {
  expect(adjust(
    -2, add(10), list
  )).toEqual(expected)
})

test('when index is out of bounds', () => {
  const list = [ 0, 1, 2, 3 ]
  expect(adjust(
    4, add(1), list
  )).toEqual(list)
  expect(adjust(
    -5, add(1), list
  )).toEqual(list)
})

all

all<T>(predicate: (x: T) => boolean, list: T[]): boolean

It returns true, if all members of array list returns true, when applied as argument to predicate function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%200%2C%201%2C%202%2C%203%2C%204%20%5D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3E%20-1%0A%0Aconst%20result%20%3D%20R.all(predicate%2C%20list)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.all</strong> example in Rambda REPL</a>

all<T>(predicate: (x: T) => boolean, list: T[]): boolean;
all<T>(predicate: (x: T) => boolean): (list: T[]) => boolean;

export function all(predicate, list){
  if (arguments.length === 1) return _list => all(predicate, _list)

  for (let i = 0; i < list.length; i++){
    if (!predicate(list[ i ])) return false
  }

  return true
}

import { all } from './all.js'

const list = [ 0, 1, 2, 3, 4 ]

test('when true', () => {
  const fn = x => x > -1

  expect(all(fn)(list)).toBeTrue()
})

test('when false', () => {
  const fn = x => x > 2

  expect(all(fn, list)).toBeFalse()
})

import {all} from 'rambda'

describe('all', () => {
  it('happy', () => {
    const result = all(
      x => {
        x // $ExpectType number
        return x > 0
      },
      [1, 2, 3]
    )
    result // $ExpectType boolean
  })
  it('curried needs a type', () => {
    const result = all<number>(x => {
      x // $ExpectType number
      return x > 0
    })([1, 2, 3])
    result // $ExpectType boolean
  })
})

allPass

allPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean

It returns true, if all functions of predicates return true, when input is their argument.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20input%20%3D%20%7B%0A%20%20a%20%3A%201%2C%0A%20%20b%20%3A%202%2C%0A%7D%0Aconst%20predicates%20%3D%20%5B%0A%20%20x%20%3D%3E%20x.a%20%3D%3D%3D%201%2C%0A%20%20x%20%3D%3E%20x.b%20%3D%3D%3D%202%2C%0A%5D%0Aconst%20result%20%3D%20R.allPass(predicates)(input)%20%2F%2F%20%3D%3E%20true">Try this <strong>R.allPass</strong> example in Rambda REPL</a>

allPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean;
allPass<T>(predicates: ((...inputs: T[]) => boolean)[]): (...inputs: T[]) => boolean;

export function allPass(predicates){
  return (...input) => {
    let counter = 0
    while (counter < predicates.length){
      if (!predicates[ counter ](...input)){
        return false
      }
      counter++
    }

    return true
  }
}

import { allPass } from './allPass.js'

test('happy', () => {
  const rules = [ x => typeof x === 'number', x => x > 10, x => x * 7 < 100 ]

  expect(allPass(rules)(11)).toBeTrue()

  expect(allPass(rules)(undefined)).toBeFalse()
})

test('when returns true', () => {
  const conditionArr = [ val => val.a === 1, val => val.b === 2 ]

  expect(allPass(conditionArr)({
    a : 1,
    b : 2,
  })).toBeTrue()
})

test('when returns false', () => {
  const conditionArr = [ val => val.a === 1, val => val.b === 3 ]

  expect(allPass(conditionArr)({
    a : 1,
    b : 2,
  })).toBeFalse()
})

test('works with multiple inputs', () => {
  const fn = function (
    w, x, y, z
  ){
    return w + x === y + z
  }
  expect(allPass([ fn ])(
    3, 3, 3, 3
  )).toBeTrue()
})

import {allPass, filter} from 'rambda'

describe('allPass', () => {
  it('happy', () => {
    const x = allPass<number>([
      y => {
        y // $ExpectType number
        return typeof y === 'number'
      },
      y => {
        return y > 0
      },
    ])(11)

    x // $ExpectType boolean
  })
  it('issue #642', () => {
    const isGreater = (num: number) => num > 5
    const pred = allPass([isGreater])
    const xs = [0, 1, 2, 3]

    const filtered1 = filter(pred)(xs)
    filtered1 // $ExpectType number[]
    const filtered2 = xs.filter(pred)
    filtered2 // $ExpectType number[]
  })
  it('issue #604', () => {
    const plusEq = function(w: number, x: number, y: number, z: number) {
      return w + x === y + z
    }
    const result = allPass([plusEq])(3, 3, 3, 3)

    result // $ExpectType boolean
  })
})

always

It returns function that always returns x.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20R.always(7)%0A%0Aconst%20result%20%3D%20fn()%0A%2F%2F%20%3D%3E%207">Try this <strong>R.always</strong> example in Rambda REPL</a>

and

Logical AND

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.and(true%2C%20true)%3B%20%2F%2F%20%3D%3E%20true%0AR.and(false%2C%20true)%3B%20%2F%2F%20%3D%3E%20false%0Aconst%20result%20%3D%20R.and(true%2C%20'foo')%3B%20%2F%2F%20%3D%3E%20'foo'">Try this <strong>R.and</strong> example in Rambda REPL</a>

any

any<T>(predicate: (x: T) => boolean, list: T[]): boolean

It returns true, if at least one member of list returns true, when passed to a predicate function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%5D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20*%20x%20%3E%208%0Aconst%20result%20%3D%20R.any(fn%2C%20list)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.any</strong> example in Rambda REPL</a>

any<T>(predicate: (x: T) => boolean, list: T[]): boolean;
any<T>(predicate: (x: T) => boolean): (list: T[]) => boolean;

export function any(predicate, list){
  if (arguments.length === 1) return _list => any(predicate, _list)

  let counter = 0
  while (counter < list.length){
    if (predicate(list[ counter ], counter)){
      return true
    }
    counter++
  }

  return false
}

import { any } from './any.js'

const list = [ 1, 2, 3 ]

test('happy', () => {
  expect(any(x => x < 0, list)).toBeFalse()
})

test('with curry', () => {
  expect(any(x => x > 2)(list)).toBeTrue()
})

import {any} from 'rambda'

describe('R.any', () => {
  it('happy', () => {
    const result = any(
      x => {
        x // $ExpectType number
        return x > 2
      },
      [1, 2, 3]
    )
    result // $ExpectType boolean
  })

  it('when curried needs a type', () => {
    const result = any<number>(x => {
      x // $ExpectType number
      return x > 2
    })([1, 2, 3])
    result // $ExpectType boolean
  })
})

anyPass

anyPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean

It accepts list of predicates and returns a function. This function with its input will return true, if any of predicates returns true for this input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20isBig%20%3D%20x%20%3D%3E%20x%20%3E%2020%0Aconst%20isOdd%20%3D%20x%20%3D%3E%20x%20%25%202%20%3D%3D%3D%201%0Aconst%20input%20%3D%2011%0A%0Aconst%20fn%20%3D%20R.anyPass(%0A%20%20%5BisBig%2C%20isOdd%5D%0A)%0A%0Aconst%20result%20%3D%20fn(input)%20%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.anyPass</strong> example in Rambda REPL</a>

anyPass<T>(predicates: ((x: T) => boolean)[]): (input: T) => boolean;
anyPass<T>(predicates: ((...inputs: T[]) => boolean)[]): (...inputs: T[]) => boolean;

export function anyPass(predicates){
  return (...input) => {
    let counter = 0
    while (counter < predicates.length){
      if (predicates[ counter ](...input)){
        return true
      }
      counter++
    }

    return false
  }
}

import { anyPass } from './anyPass.js'

test('happy', () => {
  const rules = [ x => typeof x === 'string', x => x > 10 ]
  const predicate = anyPass(rules)
  expect(predicate('foo')).toBeTrue()
  expect(predicate(6)).toBeFalse()
})

test('happy', () => {
  const rules = [ x => typeof x === 'string', x => x > 10 ]

  expect(anyPass(rules)(11)).toBeTrue()
  expect(anyPass(rules)(undefined)).toBeFalse()
})

const obj = {
  a : 1,
  b : 2,
}

test('when returns true', () => {
  const conditionArr = [ val => val.a === 1, val => val.a === 2 ]

  expect(anyPass(conditionArr)(obj)).toBeTrue()
})

test('when returns false + curry', () => {
  const conditionArr = [ val => val.a === 2, val => val.b === 3 ]

  expect(anyPass(conditionArr)(obj)).toBeFalse()
})

test('with empty predicates list', () => {
  expect(anyPass([])(3)).toBeFalse()
})

test('works with multiple inputs', () => {
  const fn = function (
    w, x, y, z
  ){
    console.log(
      w, x, y, z
    )

    return w + x === y + z
  }
  expect(anyPass([ fn ])(
    3, 3, 3, 3
  )).toBeTrue()
})

import {anyPass, filter} from 'rambda'

describe('anyPass', () => {
  it('happy', () => {
    const x = anyPass<number>([
      y => {
        y // $ExpectType number
        return typeof y === 'number'
      },
      y => {
        return y > 0
      },
    ])(11)

    x // $ExpectType boolean
  })
  it('issue #604', () => {
    const plusEq = function(w: number, x: number, y: number, z: number) {
      return w + x === y + z
    }
    const result = anyPass([plusEq])(3, 3, 3, 3)

    result // $ExpectType boolean
  })
  it('issue #642', () => {
    const isGreater = (num: number) => num > 5
    const pred = anyPass([isGreater])
    const xs = [0, 1, 2, 3]

    const filtered1 = filter(pred)(xs)
    filtered1 // $ExpectType number[]
    const filtered2 = xs.filter(pred)
    filtered2 // $ExpectType number[]
  })
  it('functions as a type guard', () => {
    const isString = (x: unknown): x is string => typeof x === 'string'
    const isNumber = (x: unknown): x is number => typeof x === 'number'
    const isBoolean = (x: unknown): x is boolean => typeof x === 'boolean'

    const isStringNumberOrBoolean = anyPass([isString, isNumber, isBoolean])

    isStringNumberOrBoolean // $ExpectType (input: unknown) => boolean

    const aValue: unknown = 1

    if (isStringNumberOrBoolean(aValue)) {
      aValue // $ExpectType unknown
    }
  })
})

ap

ap<T, U>(fns: Array<(a: T) => U>[], vs: T[]): U[]

It takes a list of functions and a list of values. Then it returns a list of values obtained by applying each function to each value.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.ap(%0A%20%20%5B%0A%20%20%20%20x%20%3D%3E%20x%20%2B%201%2C%0A%20%20%20%20x%20%3D%3E%20x%20%2B%202%2C%0A%20%20%5D%2C%0A%20%20%5B1%2C%202%2C%203%5D%0A)%0A%2F%2F%20%3D%3E%20%5B2%2C%203%2C%204%2C%203%2C%204%2C%205%5D">Try this <strong>R.ap</strong> example in Rambda REPL</a>

ap<T, U>(fns: Array<(a: T) => U>[], vs: T[]): U[];
ap<T, U>(fns: Array<(a: T) => U>): (vs: T[]) => U[];
ap<R, A, B>(fn: (r: R, a: A) => B, fn1: (r: R) => A): (r: R) => B;

export function ap(functions, input){
  if (arguments.length === 1){
    return _inputs => ap(functions, _inputs)
  }

  return functions.reduce((acc, fn) => [ ...acc, ...input.map(fn) ], [])
}

import { ap } from './ap.js'

function mult2(x){
  return x * 2
}
function plus3(x){
  return x + 3
}

test('happy', () => {
  expect(ap([ mult2, plus3 ], [ 1, 2, 3 ])).toEqual([ 2, 4, 6, 4, 5, 6 ])
})

aperture

aperture<N extends number, T>(n: N, list: T[]): Array<Tuple<T, N>> | []

It returns a new list, composed of consecutive n-tuples from a list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.aperture(2%2C%20%5B1%2C%202%2C%203%2C%204%5D)%0A%2F%2F%20%3D%3E%20%5B%5B1%2C%202%5D%2C%20%5B2%2C%203%5D%2C%20%5B3%2C%204%5D%5D">Try this <strong>R.aperture</strong> example in Rambda REPL</a>

aperture<N extends number, T>(n: N, list: T[]): Array<Tuple<T, N>> | [];
aperture<N extends number>(n: N): <T>(list: T[]) => Array<Tuple<T, N>> | [];

export function aperture(step, list){
  if (arguments.length === 1){
    return _list => aperture(step, _list)
  }
  if (step > list.length) return []
  let idx = 0
  const limit = list.length - (step - 1)
  const acc = new Array(limit)
  while (idx < limit){
    acc[ idx ] = list.slice(idx, idx + step)
    idx += 1
  }

  return acc
}

import { aperture } from './aperture.js'

const list = [ 1, 2, 3, 4, 5, 6, 7 ]

test('happy', () => {
  expect(aperture(1, list)).toEqual([ [ 1 ], [ 2 ], [ 3 ], [ 4 ], [ 5 ], [ 6 ], [ 7 ] ])
  expect(aperture(2, list)).toEqual([
    [ 1, 2 ],
    [ 2, 3 ],
    [ 3, 4 ],
    [ 4, 5 ],
    [ 5, 6 ],
    [ 6, 7 ],
  ])
  expect(aperture(3, list)).toEqual([
    [ 1, 2, 3 ],
    [ 2, 3, 4 ],
    [ 3, 4, 5 ],
    [ 4, 5, 6 ],
    [ 5, 6, 7 ],
  ])
  expect(aperture(8, list)).toEqual([])
})

append

append<T>(xToAppend: T, iterable: T[]): T[]

It adds element x at the end of iterable.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20x%20%3D%20'foo'%0A%0Aconst%20result%20%3D%20R.append(x%2C%20%5B'bar'%2C%20'baz'%5D)%0A%2F%2F%20%3D%3E%20%5B'bar'%2C%20'baz'%2C%20'foo'%5D">Try this <strong>R.append</strong> example in Rambda REPL</a>

append<T>(xToAppend: T, iterable: T[]): T[];
append<T, U>(xToAppend: T, iterable: IsFirstSubtypeOfSecond<T, U>[]) : U[];
append<T>(xToAppend: T): <U>(iterable: IsFirstSubtypeOfSecond<T, U>[]) => U[];
append<T>(xToAppend: T): (iterable: T[]) => T[];

import { cloneList } from './_internals/cloneList.js'

export function append(x, input){
  if (arguments.length === 1) return _input => append(x, _input)

  if (typeof input === 'string') return input.split('').concat(x)

  const clone = cloneList(input)
  clone.push(x)

  return clone
}

import { append } from './append.js'

test('happy', () => {
  expect(append('tests', [ 'write', 'more' ])).toEqual([
    'write',
    'more',
    'tests',
  ])
})

test('append to empty array', () => {
  expect(append('tests')([])).toEqual([ 'tests' ])
})

test('with strings', () => {
  expect(append('o', 'fo')).toEqual([ 'f', 'o', 'o' ])
})

import {append, prepend} from 'rambda'

const listOfNumbers = [1, 2, 3]
const listOfNumbersAndStrings = [1, 'b', 3]

describe('R.append/R.prepend', () => {
  describe("with the same primitive type as the array's elements", () => {
    it('uncurried', () => {
      // @ts-expect-error
      append('d', listOfNumbers)
      // @ts-expect-error
      prepend('d', listOfNumbers)
      append(4, listOfNumbers) // $ExpectType number[]
      prepend(4, listOfNumbers) // $ExpectType number[]
    })

    it('curried', () => {
      // @ts-expect-error
      append('d')(listOfNumbers)
      append(4)(listOfNumbers) // $ExpectType number[]
      prepend(4)(listOfNumbers) // $ExpectType number[]
    })
  })

  describe("with a subtype of the array's elements", () => {
    it('uncurried', () => {
      // @ts-expect-error
      append(true, listOfNumbersAndStrings)
      append(4, listOfNumbersAndStrings) // $ExpectType (string | number)[]
      prepend(4, listOfNumbersAndStrings) // $ExpectType (string | number)[]
    })

    it('curried', () => {
      // @ts-expect-error
      append(true)(listOfNumbersAndStrings)
      append(4)(listOfNumbersAndStrings) // $ExpectType (string | number)[]
      prepend(4)(listOfNumbersAndStrings) // $ExpectType (string | number)[]
    })
  })

  describe("expanding the type of the array's elements", () => {
    it('uncurried', () => {
      // @ts-expect-error
      append('d', listOfNumbers)
      append<string | number>('d', listOfNumbers) // $ExpectType (string | number)[]
      prepend<string | number>('d', listOfNumbers) // $ExpectType (string | number)[]
    })

    it('curried', () => {
      // @ts-expect-error
      append('d')(listOfNumbers)
      const appendD = append('d')
      appendD<string | number>(listOfNumbers) // $ExpectType (string | number)[]
      const prependD = prepend('d')
      prependD<string | number>(listOfNumbers) // $ExpectType (string | number)[]
    })
  })
})

apply

apply<T = any>(fn: (...args: any[]) => T, args: any[]): T

It applies function fn to the list of arguments.

This is useful for creating a fixed-arity function from a variadic function. fn should be a bound function if context is significant.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.apply(Math.max%2C%20%5B42%2C%20-Infinity%2C%201337%5D)%0A%2F%2F%20%3D%3E%201337">Try this <strong>R.apply</strong> example in Rambda REPL</a>

apply<T = any>(fn: (...args: any[]) => T, args: any[]): T;
apply<T = any>(fn: (...args: any[]) => T): (args: any[]) => T;

export function apply(fn, args){
  if (arguments.length === 1){
    return _args => apply(fn, _args)
  }

  return fn.apply(this, args)
}

import { apply } from './apply.js'
import { bind } from './bind.js'
import { identity } from './identity.js'

test('happy', () => {
  expect(apply(identity, [ 1, 2, 3 ])).toBe(1)
})

test('applies function to argument list', () => {
  expect(apply(Math.max, [ 1, 2, 3, -99, 42, 6, 7 ])).toBe(42)
})

test('provides no way to specify context', () => {
  const obj = {
    method (){
      return this === obj
    },
  }
  expect(apply(obj.method, [])).toBeFalse()
  expect(apply(bind(obj.method, obj), [])).toBeTrue()
})

import {apply, identity} from 'rambda'

describe('R.apply', () => {
  it('happy', () => {
    const result = apply<number>(identity, [1, 2, 3])

    result // $ExpectType number
  })
  it('curried', () => {
    const fn = apply<number>(identity)
    const result = fn([1, 2, 3])

    result // $ExpectType number
  })
})

applySpec

applySpec<Spec extends Record<string, AnyFunction>>(
  spec: Spec
): (
  ...args: Parameters<ValueOfRecord<Spec>>
) => { [Key in keyof Spec]: ReturnType<Spec[Key]> }

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20R.applySpec(%7B%0A%20%20sum%3A%20R.add%2C%0A%20%20nested%3A%20%7B%20mul%3A%20R.multiply%20%7D%0A%7D)%0Aconst%20result%20%3D%20fn(2%2C%204)%20%0A%2F%2F%20%3D%3E%20%7B%20sum%3A%206%2C%20nested%3A%20%7B%20mul%3A%208%20%7D%20%7D">Try this <strong>R.applySpec</strong> example in Rambda REPL</a>

applySpec<Spec extends Record<string, AnyFunction>>(
  spec: Spec
): (
  ...args: Parameters<ValueOfRecord<Spec>>
) => { [Key in keyof Spec]: ReturnType<Spec[Key]> };
applySpec<T>(spec: any): (...args: unknown[]) => T;

import { isArray } from './_internals/isArray.js'

// recursively traverse the given spec object to find the highest arity function
export function __findHighestArity(spec, max = 0){
  for (const key in spec){
    if (spec.hasOwnProperty(key) === false || key === 'constructor') continue

    if (typeof spec[ key ] === 'object'){
      max = Math.max(max, __findHighestArity(spec[ key ]))
    }

    if (typeof spec[ key ] === 'function'){
      max = Math.max(max, spec[ key ].length)
    }
  }

  return max
}

function __filterUndefined(){
  const defined = []
  let i = 0
  const l = arguments.length
  while (i < l){
    if (typeof arguments[ i ] === 'undefined') break
    defined[ i ] = arguments[ i ]
    i++
  }

  return defined
}

function __applySpecWithArity(
  spec, arity, cache
){
  const remaining = arity - cache.length

  if (remaining === 1)
    return x =>
      __applySpecWithArity(
        spec, arity, __filterUndefined(...cache, x)
      )
  if (remaining === 2)
    return (x, y) =>
      __applySpecWithArity(
        spec, arity, __filterUndefined(
          ...cache, x, y
        )
      )
  if (remaining === 3)
    return (
      x, y, z
    ) =>
      __applySpecWithArity(
        spec, arity, __filterUndefined(
          ...cache, x, y, z
        )
      )
  if (remaining === 4)
    return (
      x, y, z, a
    ) =>
      __applySpecWithArity(
        spec,
        arity,
        __filterUndefined(
          ...cache, x, y, z, a
        )
      )
  if (remaining > 4)
    return (...args) =>
      __applySpecWithArity(
        spec, arity, __filterUndefined(...cache, ...args)
      )

  // handle spec as Array
  if (isArray(spec)){
    const ret = []
    let i = 0
    const l = spec.length
    for (; i < l; i++){
      // handle recursive spec inside array
      if (typeof spec[ i ] === 'object' || isArray(spec[ i ])){
        ret[ i ] = __applySpecWithArity(
          spec[ i ], arity, cache
        )
      }
      // apply spec to the key
      if (typeof spec[ i ] === 'function'){
        ret[ i ] = spec[ i ](...cache)
      }
    }

    return ret
  }

  // handle spec as Object
  const ret = {}
  // apply callbacks to each property in the spec object
  for (const key in spec){
    if (spec.hasOwnProperty(key) === false || key === 'constructor') continue

    // apply the spec recursively
    if (typeof spec[ key ] === 'object'){
      ret[ key ] = __applySpecWithArity(
        spec[ key ], arity, cache
      )
      continue
    }

    // apply spec to the key
    if (typeof spec[ key ] === 'function'){
      ret[ key ] = spec[ key ](...cache)
    }
  }

  return ret
}

export function applySpec(spec, ...args){
  // get the highest arity spec function, cache the result and pass to __applySpecWithArity
  const arity = __findHighestArity(spec)

  if (arity === 0){
    return () => ({})
  }
  const toReturn = __applySpecWithArity(
    spec, arity, args
  )

  return toReturn
}

import { applySpec as applySpecRamda, nAry } from 'ramda'

import {
  add,
  always,
  compose,
  dec,
  inc,
  map,
  path,
  prop,
  T,
} from '../rambda.js'
import { applySpec } from './applySpec.js'

test('different than Ramda when bad spec', () => {
  const result = applySpec({ sum : { a : 1 } })(1, 2)
  const ramdaResult = applySpecRamda({ sum : { a : 1 } })(1, 2)
  expect(result).toEqual({})
  expect(ramdaResult).toEqual({ sum : { a : {} } })
})

test('works with empty spec', () => {
  expect(applySpec({})()).toEqual({})
  expect(applySpec([])(1, 2)).toEqual({})
  expect(applySpec(null)(1, 2)).toEqual({})
})

test('works with unary functions', () => {
  const result = applySpec({
    v : inc,
    u : dec,
  })(1)
  const expected = {
    v : 2,
    u : 0,
  }
  expect(result).toEqual(expected)
})

test('works with binary functions', () => {
  const result = applySpec({ sum : add })(1, 2)
  expect(result).toEqual({ sum : 3 })
})

test('works with nested specs', () => {
  const result = applySpec({
    unnested : always(0),
    nested   : { sum : add },
  })(1, 2)
  const expected = {
    unnested : 0,
    nested   : { sum : 3 },
  }
  expect(result).toEqual(expected)
})

test('works with arrays of nested specs', () => {
  const result = applySpec({
    unnested : always(0),
    nested   : [ { sum : add } ],
  })(1, 2)

  expect(result).toEqual({
    unnested : 0,
    nested   : [ { sum : 3 } ],
  })
})

test('works with arrays of spec objects', () => {
  const result = applySpec([ { sum : add } ])(1, 2)

  expect(result).toEqual([ { sum : 3 } ])
})

test('works with arrays of functions', () => {
  const result = applySpec([ map(prop('a')), map(prop('b')) ])([
    {
      a : 'a1',
      b : 'b1',
    },
    {
      a : 'a2',
      b : 'b2',
    },
  ])
  const expected = [
    [ 'a1', 'a2' ],
    [ 'b1', 'b2' ],
  ]
  expect(result).toEqual(expected)
})

test('works with a spec defining a map key', () => {
  expect(applySpec({ map : prop('a') })({ a : 1 })).toEqual({ map : 1 })
})

test('cannot retains the highest arity', () => {
  const f = applySpec({
    f1 : nAry(2, T),
    f2 : nAry(5, T),
  })
  const fRamda = applySpecRamda({
    f1 : nAry(2, T),
    f2 : nAry(5, T),
  })
  expect(f).toHaveLength(0)
  expect(fRamda).toHaveLength(5)
})

test('returns a curried function', () => {
  expect(applySpec({ sum : add })(1)(2)).toEqual({ sum : 3 })
})

// Additional tests
// ============================================
test('arity', () => {
  const spec = {
    one   : x1 => x1,
    two   : (x1, x2) => x1 + x2,
    three : (
      x1, x2, x3
    ) => x1 + x2 + x3,
  }
  expect(applySpec(
    spec, 1, 2, 3
  )).toEqual({
    one   : 1,
    two   : 3,
    three : 6,
  })
})

test('arity over 5 arguments', () => {
  const spec = {
    one   : x1 => x1,
    two   : (x1, x2) => x1 + x2,
    three : (
      x1, x2, x3
    ) => x1 + x2 + x3,
    four : (
      x1, x2, x3, x4
    ) => x1 + x2 + x3 + x4,
    five : (
      x1, x2, x3, x4, x5
    ) => x1 + x2 + x3 + x4 + x5,
  }
  expect(applySpec(
    spec, 1, 2, 3, 4, 5
  )).toEqual({
    one   : 1,
    two   : 3,
    three : 6,
    four  : 10,
    five  : 15,
  })
})

test('curried', () => {
  const spec = {
    one   : x1 => x1,
    two   : (x1, x2) => x1 + x2,
    three : (
      x1, x2, x3
    ) => x1 + x2 + x3,
  }
  expect(applySpec(spec)(1)(2)(3)).toEqual({
    one   : 1,
    two   : 3,
    three : 6,
  })
})

test('curried over 5 arguments', () => {
  const spec = {
    one   : x1 => x1,
    two   : (x1, x2) => x1 + x2,
    three : (
      x1, x2, x3
    ) => x1 + x2 + x3,
    four : (
      x1, x2, x3, x4
    ) => x1 + x2 + x3 + x4,
    five : (
      x1, x2, x3, x4, x5
    ) => x1 + x2 + x3 + x4 + x5,
  }
  expect(applySpec(spec)(1)(2)(3)(4)(5)).toEqual({
    one   : 1,
    two   : 3,
    three : 6,
    four  : 10,
    five  : 15,
  })
})

test('undefined property', () => {
  const spec = { prop : path([ 'property', 'doesnt', 'exist' ]) }
  expect(applySpec(spec, {})).toEqual({ prop : undefined })
})

test('restructure json object', () => {
  const spec = {
    id          : path('user.id'),
    name        : path('user.firstname'),
    profile     : path('user.profile'),
    doesntExist : path('user.profile.doesntExist'),
    info        : { views : compose(inc, prop('views')) },
    type        : always('playa'),
  }

  const data = {
    user : {
      id        : 1337,
      firstname : 'john',
      lastname  : 'shaft',
      profile   : 'shaft69',
    },
    views : 42,
  }

  expect(applySpec(spec, data)).toEqual({
    id          : 1337,
    name        : 'john',
    profile     : 'shaft69',
    doesntExist : undefined,
    info        : { views : 43 },
    type        : 'playa',
  })
})

import {multiply, applySpec, inc, dec, add} from 'rambda'

describe('applySpec', () => {
  it('ramda 1', () => {
    const result = applySpec({
      v: inc,
      u: dec,
    })(1)
    result // $ExpectType { v: number; u: number; }
  })
  it('ramda 1', () => {
    interface Output {
      sum: number,
      multiplied: number,
    }
    const result = applySpec<Output>({
      sum: add,
      multiplied: multiply,
    })(1, 2)

    result // $ExpectType Output
  })
})

applyTo

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.applyTo(%0A%20%201%2C%0A%20%20x%20%3D%3E%20x%20%2B%201%0A)%0A%2F%2F%20%3D%3E%202">Try this <strong>R.applyTo</strong> example in Rambda REPL</a>

ascend

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.sort(R.descend(x%20%3D%3E%20x)%2C%20%5B2%2C%201%5D)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%5D">Try this <strong>R.ascend</strong> example in Rambda REPL</a>

assoc

It makes a shallow clone of obj with setting or overriding the property prop with newValue.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.assoc('c'%2C%203%2C%20%7Ba%3A%201%2C%20b%3A%202%7D)%0A%2F%2F%20%3D%3E%20%7Ba%3A%201%2C%20b%3A%202%2C%20c%3A%203%7D">Try this <strong>R.assoc</strong> example in Rambda REPL</a>

assocPath

assocPath<Output>(path: Path, newValue: any, obj: object): Output

It makes a shallow clone of obj with setting or overriding with newValue the property found with path.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20path%20%3D%20'b.c'%0Aconst%20newValue%20%3D%202%0Aconst%20obj%20%3D%20%7B%20a%3A%201%20%7D%0A%0Aconst%20result%20%3D%20R.assocPath(path%2C%20newValue%2C%20obj)%0A%2F%2F%20%3D%3E%20%7B%20a%20%3A%201%2C%20b%20%3A%20%7B%20c%20%3A%202%20%7D%7D">Try this <strong>R.assocPath</strong> example in Rambda REPL</a>

assocPath<Output>(path: Path, newValue: any, obj: object): Output;
assocPath<Output>(path: Path, newValue: any): (obj: object) => Output;
assocPath<Output>(path: Path): (newValue: any) => (obj: object) => Output;

import { cloneList } from './_internals/cloneList.js'
import { createPath } from './_internals/createPath.js'
import { isArray } from './_internals/isArray.js'
import { isIndexInteger } from './_internals/isInteger.js'
import { assocFn } from './assoc.js'
import { curry } from './curry.js'

export function assocPathFn(
  path, newValue, input
){
  const pathArrValue = createPath(path)
  if (pathArrValue.length === 0) return newValue

  const index = pathArrValue[ 0 ]
  if (pathArrValue.length > 1){
    const condition =
      typeof input !== 'object' ||
      input === null ||
      !input.hasOwnProperty(index)

    const nextInput = condition ?
      isIndexInteger(pathArrValue[ 1 ]) ?
        [] :
        {} :
      input[ index ]

    newValue = assocPathFn(
      Array.prototype.slice.call(pathArrValue, 1),
      newValue,
      nextInput
    )
  }

  if (isIndexInteger(index) && isArray(input)){
    const arr = cloneList(input)
    arr[ index ] = newValue

    return arr
  }

  return assocFn(
    index, newValue, input
  )
}

export const assocPath = curry(assocPathFn)

import { assocPathFn } from './assocPath.js'

test('happy', () => {
  const path = 'a.c.1'
  const input = {
    a : {
      b : 1,
      c : [ 1, 2 ],
    },
  }
  assocPathFn(
    path, 3, input
  )
  expect(input).toEqual({
    a : {
      b : 1,
      c : [ 1, 2 ],
    },
  })
})

test('string can be used as path input', () => {
  const testObj = {
    a : [ { b : 1 }, { b : 2 } ],
    d : 3,
  }
  const result1 = assocPathFn(
    [ 'a', 0, 'b' ], 10, testObj
  )
  const result2 = assocPathFn(
    'a.0.b', 10, testObj
  )

  const expected = {
    a : [ { b : 10 }, { b : 2 } ],
    d : 3,
  }
  expect(result1).toEqual(expected)
  expect(result2).toEqual(expected)
})

test('difference with ramda - doesn\'t overwrite primitive values with keys in the path', () => {
  const obj = { a : 'str' }
  const result = assocPathFn(
    [ 'a', 'b' ], 42, obj
  )

  expect(result).toEqual({
    a : {
      0 : 's',
      1 : 't',
      2 : 'r',
      b : 42,
    },
  })
})

test('adds a key to an empty object', () => {
  expect(assocPathFn(
    [ 'a' ], 1, {}
  )).toEqual({ a : 1 })
})

test('adds a key to a non-empty object', () => {
  expect(assocPathFn(
    'b', 2, { a : 1 }
  )).toEqual({
    a : 1,
    b : 2,
  })
})

test('adds a nested key to a non-empty object', () => {
  expect(assocPathFn(
    'b.c', 2, { a : 1 }
  )).toEqual({
    a : 1,
    b : { c : 2 },
  })
})

test('adds a nested key to a nested non-empty object', () => {
  expect(assocPathFn('b.d',
    3,{
    a : 1,
    b : { c : 2 },
  })).toEqual({
    a : 1,
    b : {
      c : 2,
      d : 3,
    },
  })
})

test('adds a key to a non-empty object', () => {
  expect(assocPathFn('b', 2, { a : 1 })).toEqual({
    a : 1,
    b : 2,
  })
})

test('adds a nested key to a non-empty object', () => {
  expect(assocPathFn('b.c', 2, { a : 1 })).toEqual({
    a : 1,
    b : { c : 2 },
  })
})

test('changes an existing key', () => {
  expect(assocPathFn(
    'a', 2, { a : 1 }
  )).toEqual({ a : 2 })
})

test('undefined is considered an empty object', () => {
  expect(assocPathFn(
    'a', 1, undefined
  )).toEqual({ a : 1 })
})

test('null is considered an empty object', () => {
  expect(assocPathFn(
    'a', 1, null
  )).toEqual({ a : 1 })
})

test('value can be null', () => {
  expect(assocPathFn(
    'a', null, null
  )).toEqual({ a : null })
})

test('value can be undefined', () => {
  expect(assocPathFn(
    'a', undefined, null
  )).toEqual({ a : undefined })
})

test('assignment is shallow', () => {
  expect(assocPathFn(
    'a', { b : 2 }, { a : { c : 3 } }
  )).toEqual({ a : { b : 2 } })
})

test('empty array as path', () => {
  const result = assocPathFn(
    [], 3, {
      a : 1,
      b : 2,
    }
  )
  expect(result).toBe(3)
})

test('happy', () => {
  const expected = { foo : { bar : { baz : 42 } } }
  const result = assocPathFn(
    [ 'foo', 'bar', 'baz' ], 42, { foo : null }
  )
  expect(result).toEqual(expected)
})

import {assocPath} from 'rambda'

interface Output {
  a: number,
  foo: {bar: number},
}

describe('R.assocPath - user must explicitly set type of output', () => {
  it('with array as path input', () => {
    const result = assocPath<Output>(['foo', 'bar'], 2, {a: 1})

    result // $ExpectType Output
  })
  it('with string as path input', () => {
    const result = assocPath<Output>('foo.bar', 2, {a: 1})

    result // $ExpectType Output
  })
})

describe('R.assocPath - curried', () => {
  it('with array as path input', () => {
    const result = assocPath<Output>(['foo', 'bar'], 2)({a: 1})

    result // $ExpectType Output
  })
  it('with string as path input', () => {
    const result = assocPath<Output>('foo.bar', 2)({a: 1})

    result // $ExpectType Output
  })
})

binary

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.binary(%0A%20%20(a%2C%20b%2C%20c)%20%3D%3E%20a%20%2B%20b%20%2B%20c%2C%0A)(1%2C%202%2C%203%2C%204)%0A%2F%2F%20%3D%3E%203">Try this <strong>R.binary</strong> example in Rambda REPL</a>

bind

bind<F extends AnyFunction, T>(fn: F, thisObj: T): (...args: Parameters<F>) => ReturnType<F>

Creates a function that is bound to a context.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20log%20%3D%20R.bind(console.log%2C%20console)%0Aconst%20result%20%3D%20R.pipe(%0A%20%20R.assoc('a'%2C%202)%2C%20%0A%20%20R.tap(log)%2C%20%0A%20%20R.assoc('a'%2C%203)%0A)(%7Ba%3A%201%7D)%3B%20%0A%2F%2F%20%3D%3E%20result%20-%20%60%7Ba%3A%203%7D%60%0A%2F%2F%20%3D%3E%20console%20log%20-%20%60%7Ba%3A%202%7D%60">Try this <strong>R.bind</strong> example in Rambda REPL</a>

bind<F extends AnyFunction, T>(fn: F, thisObj: T): (...args: Parameters<F>) => ReturnType<F>;
bind<F extends AnyFunction, T>(fn: F): (thisObj: T) => (...args: Parameters<F>) => ReturnType<F>;

import { curryN } from './curryN.js'

export function bind(fn, thisObj){
  if (arguments.length === 1){
    return _thisObj => bind(fn, _thisObj)
  }

  return curryN(fn.length, (...args) => fn.apply(thisObj, args))
}

import { bind } from './bind.js'

function Foo(x){
  this.x = x
}
function add(x){
  return this.x + x
}
function Bar(x, y){
  this.x = x
  this.y = y
}
Bar.prototype = new Foo()
Bar.prototype.getX = function (){
  return 'prototype getX'
}

test('returns a function', () => {
  expect(typeof bind(add)(Foo)).toBe('function')
})

test('returns a function bound to the specified context object', () => {
  const f = new Foo(12)
  function isFoo(){
    return this instanceof Foo
  }
  const isFooBound = bind(isFoo, f)
  expect(isFoo()).toBeFalse()
  expect(isFooBound()).toBeTrue()
})

test('works with built-in types', () => {
  const abc = bind(String.prototype.toLowerCase, 'ABCDEFG')
  expect(typeof abc).toBe('function')
  expect(abc()).toBe('abcdefg')
})

test('works with user-defined types', () => {
  const f = new Foo(12)
  function getX(){
    return this.x
  }
  const getXFooBound = bind(getX, f)
  expect(getXFooBound()).toBe(12)
})

test('works with plain objects', () => {
  const pojso = { x : 100 }
  function incThis(){
    return this.x + 1
  }
  const incPojso = bind(incThis, pojso)
  expect(typeof incPojso).toBe('function')
  expect(incPojso()).toBe(101)
})

test('does not interfere with existing object methods', () => {
  const b = new Bar('a', 'b')
  function getX(){
    return this.x
  }
  const getXBarBound = bind(getX, b)
  expect(b.getX()).toBe('prototype getX')
  expect(getXBarBound()).toBe('a')
})

test('preserves arity', () => {
  const f0 = function (){
    return 0
  }
  const f1 = function (a){
    return a
  }
  const f2 = function (a, b){
    return a + b
  }
  const f3 = function (
    a, b, c
  ){
    return a + b + c
  }

  expect(bind(f0, {})).toHaveLength(0)
  expect(bind(f1, {})).toHaveLength(1)
  expect(bind(f2, {})).toHaveLength(2)
  expect(bind(f3, {})).toHaveLength(3)
})

import {bind} from 'rambda'

class Foo {}
function isFoo<T = any>(this: T): boolean {
  return this instanceof Foo
}

describe('R.bind', () => {
  it('happy', () => {
    const foo = new Foo()
    const result = bind(isFoo, foo)()

    result // $ExpectType boolean
  })
})

both

both(pred1: Pred, pred2: Pred): Pred

It returns a function with input argument.

This function will return true, if both firstCondition and secondCondition return true when input is passed as their argument.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20firstCondition%20%3D%20x%20%3D%3E%20x%20%3E%2010%0Aconst%20secondCondition%20%3D%20x%20%3D%3E%20x%20%3C%2020%0Aconst%20fn%20%3D%20R.both(firstCondition%2C%20secondCondition)%0A%0Aconst%20result%20%3D%20%5Bfn(15)%2C%20fn(30)%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.both</strong> example in Rambda REPL</a>

both(pred1: Pred, pred2: Pred): Pred;
both<T>(pred1: Predicate<T>, pred2: Predicate<T>): Predicate<T>;
both<T>(pred1: Predicate<T>): (pred2: Predicate<T>) => Predicate<T>;
both(pred1: Pred): (pred2: Pred) => Pred;

export function both(f, g){
  if (arguments.length === 1) return _g => both(f, _g)

  return (...input) => f(...input) && g(...input)
}

import { both } from './both.js'

const firstFn = val => val > 0
const secondFn = val => val < 10

test('with curry', () => {
  expect(both(firstFn)(secondFn)(17)).toBeFalse()
})

test('without curry', () => {
  expect(both(firstFn, secondFn)(7)).toBeTrue()
})

test('with multiple inputs', () => {
  const between = function (
    a, b, c
  ){
    return a < b && b < c
  }
  const total20 = function (
    a, b, c
  ){
    return a + b + c === 20
  }
  const fn = both(between, total20)
  expect(fn(
    5, 7, 8
  )).toBeTrue()
})

test('skip evaluation of the second expression', () => {
  let effect = 'not evaluated'
  const F = function (){
    return false
  }
  const Z = function (){
    effect = 'Z got evaluated'
  }
  both(F, Z)()

  expect(effect).toBe('not evaluated')
})

import {both} from 'rambda'

describe('R.both', () => {
  it('with passed type', () => {
    const fn = both<number>(
      x => x > 1,
      x => x % 2 === 0
    )
    fn // $ExpectType Predicate<number>
    const result = fn(2) // $ExpectType boolean
    result // $ExpectType boolean
  })
  it('with passed type - curried', () => {
    const fn = both<number>(x => x > 1)(x => x % 2 === 0)
    fn // $ExpectType Predicate<number>
    const result = fn(2)
    result // $ExpectType boolean
  })
  it('no type passed', () => {
    const fn = both(
      x => {
        x // $ExpectType any
        return x > 1
      },
      x => {
        x // $ExpectType any
        return x % 2 === 0
      }
    )
    const result = fn(2)
    result // $ExpectType boolean
  })
  it('no type passed - curried', () => {
    const fn = both((x: number) => {
      x // $ExpectType number
      return x > 1
    })((x: number) => {
      x // $ExpectType number
      return x % 2 === 0
    })
    const result = fn(2)
    result // $ExpectType boolean
  })
})

call

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.call(%0A%20%20(a%2C%20b)%20%3D%3E%20a%20%2B%20b%2C%0A%20%201%2C%0A%20%202%0A)%0A%2F%2F%20%3D%3E%203">Try this <strong>R.call</strong> example in Rambda REPL</a>

chain

chain<T, U>(fn: (n: T) => U[], list: T[]): U[]

The method is also known as flatMap.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20duplicate%20%3D%20n%20%3D%3E%20%5B%20n%2C%20n%20%5D%0Aconst%20list%20%3D%20%5B%201%2C%202%2C%203%20%5D%0A%0Aconst%20result%20%3D%20chain(duplicate%2C%20list)%0A%2F%2F%20%3D%3E%20%5B%201%2C%201%2C%202%2C%202%2C%203%2C%203%20%5D">Try this <strong>R.chain</strong> example in Rambda REPL</a>

chain<T, U>(fn: (n: T) => U[], list: T[]): U[];
chain<T, U>(fn: (n: T) => U[]): (list: T[]) => U[];

export function chain(fn, list){
  if (arguments.length === 1){
    return _list => chain(fn, _list)
  }

  return [].concat(...list.map(fn))
}

import { chain as chainRamda } from 'ramda'

import { chain } from './chain.js'

const duplicate = n => [ n, n ]

test('happy', () => {
  const fn = x => [ x * 2 ]
  const list = [ 1, 2, 3 ]

  const result = chain(fn, list)

  expect(result).toEqual([ 2, 4, 6 ])
})

test('maps then flattens one level', () => {
  expect(chain(duplicate, [ 1, 2, 3 ])).toEqual([ 1, 1, 2, 2, 3, 3 ])
})

test('maps then flattens one level - curry', () => {
  expect(chain(duplicate)([ 1, 2, 3 ])).toEqual([ 1, 1, 2, 2, 3, 3 ])
})

test('flattens only one level', () => {
  const nest = n => [ [ n ] ]
  expect(chain(nest, [ 1, 2, 3 ])).toEqual([ [ 1 ], [ 2 ], [ 3 ] ])
})

test('can compose', () => {
  function dec(x){
    return [ x - 1 ]
  }
  function times2(x){
    return [ x * 2 ]
  }

  const mdouble = chain(times2)
  const mdec = chain(dec)
  expect(mdec(mdouble([ 10, 20, 30 ]))).toEqual([ 19, 39, 59 ])
})

test('@types/ramda broken test', () => {
  const score = {
    maths   : 90,
    physics : 80,
  }

  const calculateTotal = score => {
    const { maths, physics } = score

    return maths + physics
  }

  const assocTotalToScore = (total, score) => ({
    ...score,
    total,
  })

  const calculateAndAssocTotalToScore = chainRamda(assocTotalToScore,
    calculateTotal)
  expect(() =>
    calculateAndAssocTotalToScore(score)).toThrowErrorMatchingInlineSnapshot('"fn(...) is not a function"')
})

import {chain} from 'rambda'

const list = [1, 2, 3]
const fn = (x: number) => [`${x}`, `${x}`]

describe('R.chain', () => {
  it('without passing type', () => {
    const result = chain(fn, list)
    result // $ExpectType string[]

    const curriedResult = chain(fn)(list)
    curriedResult // $ExpectType string[]
  })
})

clamp

Restrict a number input to be within min and max limits.

If input is bigger than max, then the result is max.

If input is smaller than min, then the result is min.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.clamp(0%2C%2010%2C%205)%2C%20%0A%20%20R.clamp(0%2C%2010%2C%20-1)%2C%0A%20%20R.clamp(0%2C%2010%2C%2011)%0A%5D%0A%2F%2F%20%3D%3E%20%5B5%2C%200%2C%2010%5D">Try this <strong>R.clamp</strong> example in Rambda REPL</a>

clone

It creates a deep copy of the input, which may contain (nested) Arrays and Objects, Numbers, Strings, Booleans and Dates.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20objects%20%3D%20%5B%7Ba%3A%201%7D%2C%20%7Bb%3A%202%7D%5D%3B%0Aconst%20objectsClone%20%3D%20R.clone(objects)%3B%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.equals(objects%2C%20objectsClone)%2C%0A%20%20R.equals(objects%5B0%5D%2C%20objectsClone%5B0%5D)%2C%0A%5D%20%2F%2F%20%3D%3E%20%5B%20true%2C%20true%20%5D">Try this <strong>R.clone</strong> example in Rambda REPL</a>

collectBy

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.collectBy(%0A%20%20x%20%3D%3E%20x%20%25%202%2C%0A%20%20%5B1%2C%202%2C%203%2C%204%5D%0A)%0A%2F%2F%20%3D%3E%20%5B%5B2%2C%204%5D%2C%20%5B1%2C%203%5D%5D">Try this <strong>R.collectBy</strong> example in Rambda REPL</a>

comparator

It returns a comparator function that can be used in sort method.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.sort(%0A%20%20R.comparator((a%2C%20b)%20%3D%3E%20a.x%20%3C%20b.x)%2C%0A%20%20%5B%7Bx%3A%202%7D%2C%20%7Bx%3A%201%7D%5D%0A)%0A%2F%2F%20%3D%3E%20%5B%7Bx%3A%201%7D%2C%20%7Bx%3A%202%7D%5D">Try this <strong>R.comparator</strong> example in Rambda REPL</a>

complement

It returns inverted version of origin function that accept input as argument.

The return value of inverted is the negative boolean value of origin(input).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20origin%20%3D%20x%20%3D%3E%20x%20%3E%205%0Aconst%20inverted%20%3D%20complement(origin)%0A%0Aconst%20result%20%3D%20%5B%0A%20%20origin(7)%2C%0A%20%20inverted(7)%0A%5D%20%3D%3E%20%5B%20true%2C%20false%20%5D">Try this <strong>R.complement</strong> example in Rambda REPL</a>

compose

It performs right-to-left function composition.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.compose(%0A%20%20R.map(x%20%3D%3E%20x%20*%202)%2C%0A%20%20R.filter(x%20%3D%3E%20x%20%3E%202)%0A)(%5B1%2C%202%2C%203%2C%204%5D)%0A%0A%2F%2F%20%3D%3E%20%5B6%2C%208%5D">Try this <strong>R.compose</strong> example in Rambda REPL</a>

composeWith

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.composeWith(%0A%20%20(fn%2C%20intermediateResult)%20%3D%3E%20fn(intermediateResult)%2C%0A%20%20%5B%0A%20%20%20%20R.map(x%20%3D%3E%20x%20%2B%201)%2C%0A%20%20%20%20R.map(x%20%3D%3E%20x%20*%202)%2C%0A%20%20%5D%0A)(%5B1%2C%202%2C%203%5D)%0A%2F%2F%20%3D%3E%20%5B3%2C%205%2C%207%5D">Try this <strong>R.composeWith</strong> example in Rambda REPL</a>

concat

It returns a new string or array, which is the result of merging x and y.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.concat(%5B1%2C%202%5D)(%5B3%2C%204%5D)%20%2F%2F%20%3D%3E%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20result%20%3D%20R.concat('foo'%2C%20'bar')%20%2F%2F%20%3D%3E%20'foobar'">Try this <strong>R.concat</strong> example in Rambda REPL</a>

cond

It takes list with conditions and returns a new function fn that expects input as argument.

This function will start evaluating the conditions in order to find the first winner(order of conditions matter).

The winner is this condition, which left side returns true when input is its argument. Then the evaluation of the right side of the winner will be the final result.

If no winner is found, then fn returns undefined.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20R.cond(%5B%0A%20%20%5B%20x%20%3D%3E%20x%20%3E%2025%2C%20R.always('more%20than%2025')%20%5D%2C%0A%20%20%5B%20x%20%3D%3E%20x%20%3E%2015%2C%20R.always('more%20than%2015')%20%5D%2C%0A%20%20%5B%20R.T%2C%20x%20%3D%3E%20%60%24%7Bx%7D%20is%20nothing%20special%60%20%5D%2C%0A%5D)%0A%0Aconst%20result%20%3D%20%5B%0A%20%20fn(30)%2C%0A%20%20fn(20)%2C%0A%20%20fn(10)%2C%0A%5D%20%0A%2F%2F%20%3D%3E%20%5B'more%20than%2025'%2C%20'more%20than%2015'%2C%20'10%20is%20nothing%20special'%5D">Try this <strong>R.cond</strong> example in Rambda REPL</a>

converge

Accepts a converging function and a list of branching functions and returns a new function. When invoked, this new function is applied to some arguments, each branching function is applied to those same arguments. The results of each branching function are passed as arguments to the converging function to produce the return value.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.converge(R.multiply)(%5B%20R.add(1)%2C%20R.add(3)%20%5D)(2)%0A%2F%2F%20%3D%3E%2015">Try this <strong>R.converge</strong> example in Rambda REPL</a>

count

It counts how many times predicate function returns true, when supplied with iteration of list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%7Ba%3A%201%7D%2C%201%2C%20%7Ba%3A2%7D%5D%0Aconst%20result%20%3D%20R.count(x%20%3D%3E%20x.a%20!%3D%3D%20undefined%2C%20list)%0A%2F%2F%20%3D%3E%202">Try this <strong>R.count</strong> example in Rambda REPL</a>

countBy

countBy<T extends unknown>(transformFn: (x: T) => any, list: T[]): Record<string, number>

It counts elements in a list after each instance of the input list is passed through transformFn function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%20'a'%2C%20'A'%2C%20'b'%2C%20'B'%2C%20'c'%2C%20'C'%20%5D%0A%0Aconst%20result%20%3D%20countBy(R.toLower%2C%20list)%0Aconst%20expected%20%3D%20%7B%20a%3A%202%2C%20b%3A%202%2C%20c%3A%202%20%7D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.countBy</strong> example in Rambda REPL</a>

countBy<T extends unknown>(transformFn: (x: T) => any, list: T[]): Record<string, number>;
countBy<T extends unknown>(transformFn: (x: T) => any): (list: T[]) => Record<string, number>;

export function countBy(fn, list){
  if (arguments.length === 1){
    return _list => countBy(fn, _list)
  }
  const willReturn = {}

  list.forEach(item => {
    const key = fn(item)
    if (!willReturn[ key ]){
      willReturn[ key ] = 1
    } else {
      willReturn[ key ]++
    }
  })

  return willReturn
}

import { countBy } from './countBy.js'

const list = [ 'a', 'A', 'b', 'B', 'c', 'C' ]

test('happy', () => {
  const result = countBy(x => x.toLowerCase(), list)
  expect(result).toEqual({
    a : 2,
    b : 2,
    c : 2,
  })
})

import {countBy} from 'rambda'

const transformFn = (x: string) => x.toLowerCase()
const list = ['a', 'A', 'b', 'B', 'c', 'C']

describe('R.countBy', () => {
  it('happy', () => {
    const result = countBy(transformFn, list)

    result // $ExpectType Record<string, number>
  })
  it('curried', () => {
    const result = countBy(transformFn)(list)

    result // $ExpectType Record<string, number>
  })
})

curry

It expects a function as input and returns its curried version.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20(a%2C%20b%2C%20c)%20%3D%3E%20a%20%2B%20b%20%2B%20c%0Aconst%20curried%20%3D%20R.curry(fn)%0Aconst%20sum%20%3D%20curried(1%2C2)%0A%0Aconst%20result%20%3D%20sum(3)%20%2F%2F%20%3D%3E%206">Try this <strong>R.curry</strong> example in Rambda REPL</a>

curryN

It returns a curried equivalent of the provided function, with the specified arity.

dec

It decrements a number.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.dec(2)%20%2F%2F%20%3D%3E%201">Try this <strong>R.dec</strong> example in Rambda REPL</a>

defaultTo

defaultTo<T>(defaultValue: T, input: T | null | undefined): T

It returns defaultValue, if all of inputArguments are undefined, null or NaN.

Else, it returns the first truthy inputArguments instance(from left to right).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.defaultTo('foo'%2C%20'bar')%20%2F%2F%20%3D%3E%20'bar'%0AR.defaultTo('foo'%2C%20undefined)%20%2F%2F%20%3D%3E%20'foo'%0A%0A%2F%2F%20Important%20-%20emtpy%20string%20is%20not%20falsy%20value(same%20as%20Ramda)%0Aconst%20result%20%3D%20R.defaultTo('foo'%2C%20'')%20%2F%2F%20%3D%3E%20'foo'">Try this <strong>R.defaultTo</strong> example in Rambda REPL</a>

defaultTo<T>(defaultValue: T, input: T | null | undefined): T;
defaultTo<T>(defaultValue: T): (input: T | null | undefined) => T;

function isFalsy(input){
  return (
    input === undefined || input === null || Number.isNaN(input) === true
  )
}

export function defaultTo(defaultArgument, input){
  if (arguments.length === 1){
    return _input => defaultTo(defaultArgument, _input)
  }

  return isFalsy(input) ? defaultArgument : input
}

import { defaultTo } from './defaultTo.js'

test('with undefined', () => {
  expect(defaultTo('foo')(undefined)).toBe('foo')
})

test('with null', () => {
  expect(defaultTo('foo')(null)).toBe('foo')
})

test('with NaN', () => {
  expect(defaultTo('foo')(NaN)).toBe('foo')
})

test('with empty string', () => {
  expect(defaultTo('foo', '')).toBe('')
})

test('with false', () => {
  expect(defaultTo('foo', false)).toBeFalse()
})

test('when inputArgument passes initial check', () => {
  expect(defaultTo('foo', 'bar')).toBe('bar')
})

import {defaultTo} from 'rambda'

describe('R.defaultTo with Ramda spec', () => {
  it('happy', () => {
    const result = defaultTo('foo', '')
    result // $ExpectType "" | "foo"
  })
  it('with explicit type', () => {
    const result = defaultTo<string>('foo', null)
    result // $ExpectType string
  })
})

descend

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.sort(R.descend(x%20%3D%3E%20x)%2C%20%5B1%2C%202%5D)%0A%2F%2F%20%3D%3E%20%5B2%2C%201%5D">Try this <strong>R.descend</strong> example in Rambda REPL</a>

difference

difference<T>(a: T[], b: T[]): T[]

It returns the uniq set of all elements in the first list a not contained in the second list b.

R.equals is used to determine equality.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20a%20%3D%20%5B%201%2C%202%2C%203%2C%204%20%5D%0Aconst%20b%20%3D%20%5B%203%2C%204%2C%205%2C%206%20%5D%0A%0Aconst%20result%20%3D%20R.difference(a%2C%20b)%0A%2F%2F%20%3D%3E%20%5B%201%2C%202%20%5D">Try this <strong>R.difference</strong> example in Rambda REPL</a>

difference<T>(a: T[], b: T[]): T[];
difference<T>(a: T[]): (b: T[]) => T[];

import { includes } from './includes.js'
import { uniq } from './uniq.js'

export function difference(a, b){
  if (arguments.length === 1) return _b => difference(a, _b)

  return uniq(a).filter(aInstance => !includes(aInstance, b))
}

import { difference as differenceRamda } from 'ramda'

import { difference } from './difference.js'

test('difference', () => {
  const a = [ 1, 2, 3, 4 ]
  const b = [ 3, 4, 5, 6 ]
  expect(difference(a)(b)).toEqual([ 1, 2 ])

  expect(difference([], [])).toEqual([])
})

test('difference with objects', () => {
  const a = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ]
  const b = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ]
  expect(difference(a, b)).toEqual([ { id : 1 }, { id : 2 } ])
})

test('no duplicates in first list', () => {
  const M2 = [ 1, 2, 3, 4, 1, 2, 3, 4 ]
  const N2 = [ 3, 3, 4, 4, 5, 5, 6, 6 ]
  expect(difference(M2, N2)).toEqual([ 1, 2 ])
})

test('should use R.equals', () => {
  expect(difference([ 1 ], [ 1 ])).toHaveLength(0)
  expect(differenceRamda([ NaN ], [ NaN ])).toHaveLength(0)
})

import {difference} from 'rambda'

const list1 = [1, 2, 3]
const list2 = [1, 2, 4]

describe('R.difference', () => {
  it('happy', () => {
    const result = difference(list1, list2)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = difference(list1)(list2)

    result // $ExpectType number[]
  })
})

differenceWith

differenceWith<T1, T2>(
  pred: (a: T1, b: T2) => boolean,
  list1: T1[],
  list2: T2[],
): T1[]

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.differenceWith(%0A%20%20(a%2C%20b)%20%3D%3E%20a.x%20%3D%3D%3D%20b.x%2C%0A%20%20%5B%7Bx%3A%201%7D%2C%20%7Bx%3A%202%7D%5D%2C%0A%20%20%5B%7Bx%3A%201%7D%2C%20%7Bx%3A%203%7D%5D%0A)%0A%2F%2F%20%3D%3E%20%5B%7Bx%3A%202%7D%5D">Try this <strong>R.differenceWith</strong> example in Rambda REPL</a>

differenceWith<T1, T2>(
  pred: (a: T1, b: T2) => boolean,
  list1: T1[],
  list2: T2[],
): T1[];
differenceWith<T1, T2>(
  pred: (a: T1, b: T2) => boolean,
): (list1: T1[], list2: T2[]) => T1[];
differenceWith<T1, T2>(
  pred: (a: T1, b: T2) => boolean,
  list1: T1[],
): (list2: T2[]) => T1[];

import { curry } from './curry.js'
import { _indexOf } from './equals.js'

export function differenceWithFn(
  fn, a, b
){
  const willReturn = []
  const [ first, second ] = a.length >= b.length ? [ a, b ] : [ b, a ]

  first.forEach(item => {
    const hasItem = second.some(secondItem => fn(item, secondItem))
    if (!hasItem && _indexOf(item, willReturn) === -1){
      willReturn.push(item)
    }
  })

  return willReturn
}

export const differenceWith = curry(differenceWithFn)

import { differenceWith } from './differenceWith.js';

const fn = (a, b) => a.x === b.x;

test('same length of list', () => {
	const result = differenceWith(fn, [{ x: 1 }, { x: 2 }], [{ x: 1 }, { x: 3 }]);
	expect(result).toEqual([{ x: 2 }]);
});

test('different length of list', () => {
	const foo = [{ x: 1 }, { x: 2 }, { x: 3 }];
	const bar = [{ x: 3 }, { x: 4 }];
	const result = differenceWith(fn, foo, bar);
	expect(result).toEqual([{ x: 1 }, { x: 2 }]);
});

dissoc

It returns a new object that does not contain property prop.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.dissoc('b'%2C%20%7Ba%3A%201%2C%20b%3A%202%2C%20c%3A%203%7D)%0A%2F%2F%20%3D%3E%20%7Ba%3A%201%2C%20c%3A%203%7D">Try this <strong>R.dissoc</strong> example in Rambda REPL</a>

dissocPath

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.dissocPath(%5B'a'%2C%20'b'%5D%2C%20%7Ba%3A%20%7Bb%3A%201%2C%20c%3A%202%7D%7D)%0A%2F%2F%20%3D%3E%20%7Ba%3A%20%7Bc%3A%202%7D%7D">Try this <strong>R.dissocPath</strong> example in Rambda REPL</a>

divide

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.divide(71%2C%20100)%20%2F%2F%20%3D%3E%200.71">Try this <strong>R.divide</strong> example in Rambda REPL</a>

drop

drop<T>(howMany: number, input: T[]): T[]

It returns howMany items dropped from beginning of list or string input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.drop(2%2C%20%5B'foo'%2C%20'bar'%2C%20'baz'%5D)%20%2F%2F%20%3D%3E%20%5B'baz'%5D%0Aconst%20result%20%3D%20R.drop(2%2C%20'foobar')%20%20%2F%2F%20%3D%3E%20'obar'">Try this <strong>R.drop</strong> example in Rambda REPL</a>

drop<T>(howMany: number, input: T[]): T[];
drop(howMany: number, input: string): string;
drop<T>(howMany: number): {
  <T>(input: T[]): T[];
  (input: string): string;
};

export function drop(howManyToDrop, listOrString){
  if (arguments.length === 1) return _list => drop(howManyToDrop, _list)

  return listOrString.slice(howManyToDrop > 0 ? howManyToDrop : 0)
}

import assert from 'assert'

import { drop } from './drop.js'

test('with array', () => {
  expect(drop(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'baz' ])
  expect(drop(3, [ 'foo', 'bar', 'baz' ])).toEqual([])
  expect(drop(4, [ 'foo', 'bar', 'baz' ])).toEqual([])
})

test('with string', () => {
  expect(drop(3, 'rambda')).toBe('bda')
})

test('with non-positive count', () => {
  expect(drop(0, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
  expect(drop(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
  expect(drop(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
})

test('should return copy', () => {
  const xs = [ 1, 2, 3 ]

  assert.notStrictEqual(drop(0, xs), xs)
  assert.notStrictEqual(drop(-1, xs), xs)
})

import {drop} from 'rambda'

const list = [1, 2, 3, 4]
const str = 'foobar'
const howMany = 2

describe('R.drop - array', () => {
  it('happy', () => {
    const result = drop(howMany, list)
    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = drop(howMany)(list)
    result // $ExpectType number[]
  })
})

describe('R.drop - string', () => {
  it('happy', () => {
    const result = drop(howMany, str)
    result // $ExpectType string
  })
  it('curried', () => {
    const result = drop(howMany)(str)
    result // $ExpectType string
  })
})

dropLast

dropLast<T>(howMany: number, input: T[]): T[]

It returns howMany items dropped from the end of list or string input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.dropLast(2%2C%20%5B'foo'%2C%20'bar'%2C%20'baz'%5D)%20%2F%2F%20%3D%3E%20%5B'foo'%5D%0Aconst%20result%20%3D%20R.dropLast(2%2C%20'foobar')%20%20%2F%2F%20%3D%3E%20'foob'">Try this <strong>R.dropLast</strong> example in Rambda REPL</a>

dropLast<T>(howMany: number, input: T[]): T[];
dropLast(howMany: number, input: string): string;
dropLast<T>(howMany: number): {
  <T>(input: T[]): T[];
  (input: string): string;
};

export function dropLast(howManyToDrop, listOrString){
  if (arguments.length === 1){
    return _listOrString => dropLast(howManyToDrop, _listOrString)
  }

  return howManyToDrop > 0 ?
    listOrString.slice(0, -howManyToDrop) :
    listOrString.slice()
}

import assert from 'assert'

import { dropLast } from './dropLast.js'

test('with array', () => {
  expect(dropLast(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'foo' ])
  expect(dropLast(3, [ 'foo', 'bar', 'baz' ])).toEqual([])
  expect(dropLast(4, [ 'foo', 'bar', 'baz' ])).toEqual([])
})

test('with string', () => {
  expect(dropLast(3, 'rambda')).toBe('ram')
})

test('with non-positive count', () => {
  expect(dropLast(0, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
  expect(dropLast(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
  expect(dropLast(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
})

test('should return copy', () => {
  const xs = [ 1, 2, 3 ]

  assert.notStrictEqual(dropLast(0, xs), xs)
  assert.notStrictEqual(dropLast(-1, xs), xs)
})

import {dropLast} from 'rambda'

const list = [1, 2, 3, 4]
const str = 'foobar'
const howMany = 2

describe('R.dropLast - array', () => {
  it('happy', () => {
    const result = dropLast(howMany, list)
    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = dropLast(howMany)(list)
    result // $ExpectType number[]
  })
})

describe('R.dropLast - string', () => {
  it('happy', () => {
    const result = dropLast(howMany, str)
    result // $ExpectType string
  })
  it('curried', () => {
    const result = dropLast(howMany)(str)
    result // $ExpectType string
  })
})

dropLastWhile

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%2C%205%5D%3B%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3E%3D%203%0A%0Aconst%20result%20%3D%20dropLastWhile(predicate%2C%20list)%3B%0A%2F%2F%20%3D%3E%20%5B1%2C%202%5D">Try this <strong>R.dropLastWhile</strong> example in Rambda REPL</a>

dropRepeats

dropRepeats<T>(list: T[]): T[]

It removes any successive duplicates according to R.equals.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.dropRepeats(%5B%0A%20%201%2C%20%0A%20%201%2C%20%0A%20%20%7Ba%3A%201%7D%2C%20%0A%20%20%7Ba%3A1%7D%2C%20%0A%20%201%0A%5D)%0A%2F%2F%20%3D%3E%20%5B1%2C%20%7Ba%3A%201%7D%2C%201%5D">Try this <strong>R.dropRepeats</strong> example in Rambda REPL</a>

dropRepeats<T>(list: T[]): T[];

import { isArray } from './_internals/isArray.js'
import { equals } from './equals.js'

export function dropRepeats(list){
  if (!isArray(list)){
    throw new Error(`${ list } is not a list`)
  }

  const toReturn = []

  list.reduce((prev, current) => {
    if (!equals(prev, current)){
      toReturn.push(current)
    }

    return current
  }, undefined)

  return toReturn
}

import { dropRepeats as dropRepeatsRamda } from 'ramda'

import { compareCombinations } from './_internals/testUtils.js'
import { add } from './add.js'
import { dropRepeats } from './dropRepeats.js'

const list = [ 1, 2, 2, 2, 3, 4, 4, 5, 5, 3, 2, 2, { a : 1 }, { a : 1 } ]
const listClean = [ 1, 2, 3, 4, 5, 3, 2, { a : 1 } ]

test('happy', () => {
  const result = dropRepeats(list)
  expect(result).toEqual(listClean)
})

const possibleLists = [
  [ add(1), async () => {}, [ 1 ], [ 1 ], [ 2 ], [ 2 ] ],
  [ add(1), add(1), add(2) ],
  [],
  1,
  /foo/g,
  Promise.resolve(1),
]

describe('brute force', () => {
  compareCombinations({
    firstInput : possibleLists,
    callback   : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
        {
          "ERRORS_MESSAGE_MISMATCH": 0,
          "ERRORS_TYPE_MISMATCH": 0,
          "RESULTS_MISMATCH": 1,
          "SHOULD_NOT_THROW": 3,
          "SHOULD_THROW": 0,
          "TOTAL_TESTS": 6,
        }
      `)
    },
    fn      : dropRepeats,
    fnRamda : dropRepeatsRamda,
  })
})

import {dropRepeats} from 'rambda'

describe('R.dropRepeats', () => {
  it('happy', () => {
    const result = dropRepeats([1, 2, 2, 3])

    result // $ExpectType number[]
  })
})

dropRepeatsBy

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.dropRepeatsBy(%0A%20%20Math.abs%2C%0A%20%20%5B1%2C%20-1%2C%202%2C%203%2C%20-3%5D%0A)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%2C%203%5D">Try this <strong>R.dropRepeatsBy</strong> example in Rambda REPL</a>

dropRepeatsWith

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%7Ba%3A1%2Cb%3A2%7D%2C%20%7Ba%3A1%2Cb%3A3%7D%2C%20%7Ba%3A2%2C%20b%3A4%7D%5D%0Aconst%20result%20%3D%20R.dropRepeatsWith(R.prop('a')%2C%20list)%0A%0A%2F%2F%20%3D%3E%20%5B%7Ba%3A1%2Cb%3A2%7D%2C%20%7Ba%3A2%2C%20b%3A4%7D%5D">Try this <strong>R.dropRepeatsWith</strong> example in Rambda REPL</a>

dropWhile

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3C%203%0Aconst%20result%20%3D%20R.dropWhile(predicate%2C%20list)%0A%2F%2F%20%3D%3E%20%5B3%2C%204%5D">Try this <strong>R.dropWhile</strong> example in Rambda REPL</a>

either

either(firstPredicate: Pred, secondPredicate: Pred): Pred

It returns a new predicate function from firstPredicate and secondPredicate inputs.

This predicate function will return true, if any of the two input predicates return true.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20firstPredicate%20%3D%20x%20%3D%3E%20x%20%3E%2010%0Aconst%20secondPredicate%20%3D%20x%20%3D%3E%20x%20%25%202%20%3D%3D%3D%200%0Aconst%20predicate%20%3D%20R.either(firstPredicate%2C%20secondPredicate)%0A%0Aconst%20result%20%3D%20%5B%0A%20%20predicate(15)%2C%0A%20%20predicate(8)%2C%0A%20%20predicate(7)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%2C%20false%5D">Try this <strong>R.either</strong> example in Rambda REPL</a>

either(firstPredicate: Pred, secondPredicate: Pred): Pred;
either<T>(firstPredicate: Predicate<T>, secondPredicate: Predicate<T>): Predicate<T>;
either<T>(firstPredicate: Predicate<T>): (secondPredicate: Predicate<T>) => Predicate<T>;
either(firstPredicate: Pred): (secondPredicate: Pred) => Pred;

export function either(firstPredicate, secondPredicate){
  if (arguments.length === 1){
    return _secondPredicate => either(firstPredicate, _secondPredicate)
  }

  return (...input) =>
    Boolean(firstPredicate(...input) || secondPredicate(...input))
}

import { either } from './either.js'

test('with multiple inputs', () => {
  const between = function (
    a, b, c
  ){
    return a < b && b < c
  }
  const total20 = function (
    a, b, c
  ){
    return a + b + c === 20
  }
  const fn = either(between, total20)
  expect(fn(
    7, 8, 5
  )).toBeTrue()
})

test('skip evaluation of the second expression', () => {
  let effect = 'not evaluated'
  const F = function (){
    return true
  }
  const Z = function (){
    effect = 'Z got evaluated'
  }
  either(F, Z)()

  expect(effect).toBe('not evaluated')
})

test('case 1', () => {
  const firstFn = val => val > 0
  const secondFn = val => val * 5 > 10

  expect(either(firstFn, secondFn)(1)).toBeTrue()
})

test('case 2', () => {
  const firstFn = val => val > 0
  const secondFn = val => val === -10
  const fn = either(firstFn)(secondFn)

  expect(fn(-10)).toBeTrue()
})

import {either} from 'rambda'

describe('R.either', () => {
  it('with passed type', () => {
    const fn = either<number>(
      x => x > 1,
      x => x % 2 === 0
    )
    fn // $ExpectType Predicate<number>
    const result = fn(2) // $ExpectType boolean
    result // $ExpectType boolean
  })
  it('with passed type - curried', () => {
    const fn = either<number>(x => x > 1)(x => x % 2 === 0)
    fn // $ExpectType Predicate<number>
    const result = fn(2)
    result // $ExpectType boolean
  })
  it('no type passed', () => {
    const fn = either(
      x => {
        x // $ExpectType any
        return x > 1
      },
      x => {
        x // $ExpectType any
        return x % 2 === 0
      }
    )
    const result = fn(2)
    result // $ExpectType boolean
  })
  it('no type passed - curried', () => {
    const fn = either((x: number) => {
      x // $ExpectType number
      return x > 1
    })((x: number) => {
      x // $ExpectType number
      return x % 2 === 0
    })
    const result = fn(2)
    result // $ExpectType boolean
  })
})

empty

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5BR.empty(%5B1%2C2%2C3%5D)%2C%20R.empty('foo')%2C%20R.empty(%7Bx%3A%201%2C%20y%3A%202%7D)%5D%0A%2F%2F%20%3D%3E%20%5B%5B%5D%2C%20''%2C%20%7B%7D%5D">Try this <strong>R.empty</strong> example in Rambda REPL</a>

endsWith

endsWith<T extends string>(question: T, str: string): boolean

When iterable is a string, then it behaves as String.prototype.endsWith. When iterable is a list, then it uses R.equals to determine if the target list ends in the same way as the given target.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20str%20%3D%20'foo-bar'%0Aconst%20list%20%3D%20%5B%7Ba%3A1%7D%2C%20%7Ba%3A2%7D%2C%20%7Ba%3A3%7D%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.endsWith('bar'%2C%20str)%2C%0A%20%20R.endsWith(%5B%7Ba%3A1%7D%2C%20%7Ba%3A2%7D%5D%2C%20list)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%5D">Try this <strong>R.endsWith</strong> example in Rambda REPL</a>

endsWith<T extends string>(question: T, str: string): boolean;
endsWith<T extends string>(question: T): (str: string) => boolean;
endsWith<T>(question: T[], list: T[]): boolean;
endsWith<T>(question: T[]): (list: T[]) => boolean;

import { isArray } from './_internals/isArray.js'
import { equals } from './equals.js'

export function endsWith(target, iterable){
  if (arguments.length === 1) return _iterable => endsWith(target, _iterable)

  if (typeof iterable === 'string'){
    return iterable.endsWith(target)
  }
  if (!isArray(target)) return false

  const diff = iterable.length - target.length
  let correct = true
  const filtered = target.filter((x, index) => {
    if (!correct) return false
    const result = equals(x, iterable[ index + diff ])
    if (!result) correct = false

    return result
  })

  return filtered.length === target.length
}

import { endsWith as endsWithRamda } from 'ramda'

import { compareCombinations } from './_internals/testUtils.js'
import { endsWith } from './endsWith.js'

test('with string', () => {
  expect(endsWith('bar', 'foo-bar')).toBeTrue()
  expect(endsWith('baz')('foo-bar')).toBeFalse()
})

test('use R.equals with array', () => {
  const list = [ { a : 1 }, { a : 2 }, { a : 3 } ]
  expect(endsWith({ a : 3 }, list)).toBeFalse(),
  expect(endsWith([ { a : 3 } ], list)).toBeTrue()
  expect(endsWith([ { a : 2 }, { a : 3 } ], list)).toBeTrue()
  expect(endsWith(list, list)).toBeTrue()
  expect(endsWith([ { a : 1 } ], list)).toBeFalse()
})

export const possibleTargets = [
  NaN,
  [ NaN ],
  /foo/,
  [ /foo/ ],
  Promise.resolve(1),
  [ Promise.resolve(1) ],
  Error('foo'),
  [ Error('foo') ],
]

export const possibleIterables = [
  [ Promise.resolve(1), Promise.resolve(2) ],
  [ /foo/, /bar/ ],
  [ NaN ],
  [ Error('foo'), Error('bar') ],
]

describe('brute force', () => {
  compareCombinations({
    fn          : endsWith,
    fnRamda     : endsWithRamda,
    firstInput  : possibleTargets,
    secondInput : possibleIterables,
    callback    : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
        {
          "ERRORS_MESSAGE_MISMATCH": 0,
          "ERRORS_TYPE_MISMATCH": 0,
          "RESULTS_MISMATCH": 0,
          "SHOULD_NOT_THROW": 0,
          "SHOULD_THROW": 0,
          "TOTAL_TESTS": 32,
        }
      `)
    },
  })
})

import {endsWith} from 'rambda'

describe('R.endsWith - array', () => {
  const target = [{a: 2}]
  const input = [{a: 1}, {a: 2}]
  it('happy', () => {
    const result = endsWith(target, input)
    result // $ExpectType boolean
  })
  it('curried', () => {
    const result = endsWith(target)(input)
    result // $ExpectType boolean
  })
})

describe('R.endsWith - string', () => {
  const target = 'bar'
  const input = 'foo bar'
  it('happy', () => {
    const result = endsWith(target, input)
    result // $ExpectType boolean
  })
  it('curried', () => {
    const result = endsWith(target)(input)
    result // $ExpectType boolean
  })
})

eqBy

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.eqBy(Math.abs%2C%205%2C%20-5)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.eqBy</strong> example in Rambda REPL</a>

eqProps

It returns true if property prop in obj1 is equal to property prop in obj2 according to R.equals.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj1%20%3D%20%7Ba%3A%201%2C%20b%3A2%7D%0Aconst%20obj2%20%3D%20%7Ba%3A%201%2C%20b%3A3%7D%0Aconst%20result%20%3D%20R.eqProps('a'%2C%20obj1%2C%20obj2)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.eqProps</strong> example in Rambda REPL</a>

equals

equals<T>(x: T, y: T): boolean

It deeply compares x and y and returns true if they are equal.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.equals(%0A%20%20%5B1%2C%20%7Ba%3A2%7D%2C%20%5B%7Bb%3A%203%7D%5D%5D%2C%0A%20%20%5B1%2C%20%7Ba%3A2%7D%2C%20%5B%7Bb%3A%203%7D%5D%5D%0Aconst%20result%20%3D%20)%20%2F%2F%20%3D%3E%20true">Try this <strong>R.equals</strong> example in Rambda REPL</a>

equals<T>(x: T, y: T): boolean;
equals<T>(x: T): (y: T) => boolean;

import { isArray } from './_internals/isArray.js'
import { type } from './type.js'

export function _lastIndexOf(valueToFind, list){
  if (!isArray(list))
    throw new Error(`Cannot read property 'indexOf' of ${ list }`)

  const typeOfValue = type(valueToFind)
  if (![ 'Array', 'NaN', 'Object', 'RegExp' ].includes(typeOfValue))
    return list.lastIndexOf(valueToFind)

  const { length } = list
  let index = length
  let foundIndex = -1

  while (--index > -1 && foundIndex === -1)
    if (equals(list[ index ], valueToFind))
      foundIndex = index

  return foundIndex
}

export function _indexOf(valueToFind, list){
  if (!isArray(list))
    throw new Error(`Cannot read property 'indexOf' of ${ list }`)

  const typeOfValue = type(valueToFind)
  if (![ 'Array', 'NaN', 'Object', 'RegExp' ].includes(typeOfValue))
    return list.indexOf(valueToFind)

  let index = -1
  let foundIndex = -1
  const { length } = list

  while (++index < length && foundIndex === -1)
    if (equals(list[ index ], valueToFind))
      foundIndex = index

  return foundIndex
}

function _arrayFromIterator(iter){
  const list = []
  let next
  while (!(next = iter.next()).done)
    list.push(next.value)

  return list
}

function _compareSets(a, b){
  if (a.size !== b.size)
    return false

  const aList = _arrayFromIterator(a.values())
  const bList = _arrayFromIterator(b.values())

  const filtered = aList.filter(aInstance => _indexOf(aInstance, bList) === -1)

  return filtered.length === 0
}

function compareErrors(a, b){
  if (a.message !== b.message) return false
  if (a.toString !== b.toString) return false

  return a.toString() === b.toString()
}

function parseDate(maybeDate){
  if (!maybeDate.toDateString) return [ false ]

  return [ true, maybeDate.getTime() ]
}

function parseRegex(maybeRegex){
  if (maybeRegex.constructor !== RegExp) return [ false ]

  return [ true, maybeRegex.toString() ]
}

export function equals(a, b){
  if (arguments.length === 1) return _b => equals(a, _b)

  if (Object.is(a, b)) return true

  const aType = type(a)

  if (aType !== type(b)) return false
  if (aType === 'Function')
    return a.name === undefined ? false : a.name === b.name

  if ([ 'NaN', 'Null', 'Undefined' ].includes(aType)) return true

  if ([ 'BigInt', 'Number' ].includes(aType)){
    if (Object.is(-0, a) !== Object.is(-0, b)) return false

    return a.toString() === b.toString()
  }

  if ([ 'Boolean', 'String' ].includes(aType))
    return a.toString() === b.toString()

  if (aType === 'Array'){
    const aClone = Array.from(a)
    const bClone = Array.from(b)

    if (aClone.toString() !== bClone.toString())
      return false

    let loopArrayFlag = true
    aClone.forEach((aCloneInstance, aCloneIndex) => {
      if (loopArrayFlag)
        if (
          aCloneInstance !== bClone[ aCloneIndex ] &&
          !equals(aCloneInstance, bClone[ aCloneIndex ])
        )
          loopArrayFlag = false

    })

    return loopArrayFlag
  }

  const aRegex = parseRegex(a)
  const bRegex = parseRegex(b)

  if (aRegex[ 0 ])
    return bRegex[ 0 ] ? aRegex[ 1 ] === bRegex[ 1 ] : false
  else if (bRegex[ 0 ]) return false

  const aDate = parseDate(a)
  const bDate = parseDate(b)

  if (aDate[ 0 ])
    return bDate[ 0 ] ? aDate[ 1 ] === bDate[ 1 ] : false
  else if (bDate[ 0 ]) return false

  if (a instanceof Error){
    if (!(b instanceof Error)) return false

    return compareErrors(a, b)
  }

  if (aType === 'Set')
    return _compareSets(a, b)

  if (aType === 'Object'){
    const aKeys = Object.keys(a)

    if (aKeys.length !== Object.keys(b).length)
      return false

    let loopObjectFlag = true
    aKeys.forEach(aKeyInstance => {
      if (loopObjectFlag){
        const aValue = a[ aKeyInstance ]
        const bValue = b[ aKeyInstance ]

        if (aValue !== bValue && !equals(aValue, bValue))
          loopObjectFlag = false

      }
    })

    return loopObjectFlag
  }

  return false
}

import { equals as equalsRamda } from 'ramda'

import { compareCombinations } from './_internals/testUtils.js'
import { variousTypes } from './benchmarks/_utils.js'
import { equals } from './equals.js'

test('compare functions', () => {
  function foo(){}
  function bar(){}
  const baz = () => {}

  const expectTrue = equals(foo, foo)
  const expectFalseFirst = equals(foo, bar)
  const expectFalseSecond = equals(foo, baz)

  expect(expectTrue).toBeTrue()
  expect(expectFalseFirst).toBeFalse()
  expect(expectFalseSecond).toBeFalse()
})

test('with array of objects', () => {
  const list1 = [ { a : 1 }, [ { b : 2 } ] ]
  const list2 = [ { a : 1 }, [ { b : 2 } ] ]
  const list3 = [ { a : 1 }, [ { b : 3 } ] ]

  expect(equals(list1, list2)).toBeTrue()
  expect(equals(list1, list3)).toBeFalse()
})

test('with regex', () => {
  expect(equals(/s/, /s/)).toBeTrue()
  expect(equals(/s/, /d/)).toBeFalse()
  expect(equals(/a/gi, /a/gi)).toBeTrue()
  expect(equals(/a/gim, /a/gim)).toBeTrue()
  expect(equals(/a/gi, /a/i)).toBeFalse()
})

test('not a number', () => {
  expect(equals([ NaN ], [ NaN ])).toBeTrue()
})

test('new number', () => {
  expect(equals(new Number(0), new Number(0))).toBeTrue()
  expect(equals(new Number(0), new Number(1))).toBeFalse()
  expect(equals(new Number(1), new Number(0))).toBeFalse()
})

test('new string', () => {
  expect(equals(new String(''), new String(''))).toBeTrue()
  expect(equals(new String(''), new String('x'))).toBeFalse()
  expect(equals(new String('x'), new String(''))).toBeFalse()
  expect(equals(new String('foo'), new String('foo'))).toBeTrue()
  expect(equals(new String('foo'), new String('bar'))).toBeFalse()
  expect(equals(new String('bar'), new String('foo'))).toBeFalse()
})

test('new Boolean', () => {
  expect(equals(new Boolean(true), new Boolean(true))).toBeTrue()
  expect(equals(new Boolean(false), new Boolean(false))).toBeTrue()
  expect(equals(new Boolean(true), new Boolean(false))).toBeFalse()
  expect(equals(new Boolean(false), new Boolean(true))).toBeFalse()
})

test('new Error', () => {
  expect(equals(new Error('XXX'), {})).toBeFalse()
  expect(equals(new Error('XXX'), new TypeError('XXX'))).toBeFalse()
  expect(equals(new Error('XXX'), new Error('YYY'))).toBeFalse()
  expect(equals(new Error('XXX'), new Error('XXX'))).toBeTrue()
  expect(equals(new Error('XXX'), new TypeError('YYY'))).toBeFalse()
  expect(equals(new Error('XXX'), new Error('XXX'))).toBeTrue()
})

test('with dates', () => {
  expect(equals(new Date(0), new Date(0))).toBeTrue()
  expect(equals(new Date(1), new Date(1))).toBeTrue()
  expect(equals(new Date(0), new Date(1))).toBeFalse()
  expect(equals(new Date(1), new Date(0))).toBeFalse()
  expect(equals(new Date(0), {})).toBeFalse()
  expect(equals({}, new Date(0))).toBeFalse()
})

test('ramda spec', () => {
  expect(equals({}, {})).toBeTrue()

  expect(equals({
    a : 1,
    b : 2,
  },
  {
    a : 1,
    b : 2,
  })).toBeTrue()

  expect(equals({
    a : 2,
    b : 3,
  },
  {
    a : 2,
    b : 3,
  })).toBeTrue()

  expect(equals({
    a : 2,
    b : 3,
  },
  {
    a : 3,
    b : 3,
  })).toBeFalse()

  expect(equals({
    a : 2,
    b : 3,
    c : 1,
  },
  {
    a : 2,
    b : 3,
  })).toBeFalse()
})

test('works with boolean tuple', () => {
  expect(equals([ true, false ], [ true, false ])).toBeTrue()
  expect(equals([ true, false ], [ true, true ])).toBeFalse()
})

test('works with equal objects within array', () => {
  const objFirst = {
    a : {
      b : 1,
      c : 2,
      d : [ 1 ],
    },
  }
  const objSecond = {
    a : {
      b : 1,
      c : 2,
      d : [ 1 ],
    },
  }

  const x = [ 1, 2, objFirst, null, '', [] ]
  const y = [ 1, 2, objSecond, null, '', [] ]
  expect(equals(x, y)).toBeTrue()
})

test('works with different objects within array', () => {
  const objFirst = { a : { b : 1 } }
  const objSecond = { a : { b : 2 } }

  const x = [ 1, 2, objFirst, null, '', [] ]
  const y = [ 1, 2, objSecond, null, '', [] ]
  expect(equals(x, y)).toBeFalse()
})

test('works with undefined as second argument', () => {
  expect(equals(1, undefined)).toBeFalse()

  expect(equals(undefined, undefined)).toBeTrue()
})

test('compare sets', () => {
  const toCompareDifferent = new Set([ { a : 1 }, { a : 2 } ])
  const toCompareSame = new Set([ { a : 1 }, { a : 2 }, { a : 1 } ])
  const testSet = new Set([ { a : 1 }, { a : 2 }, { a : 1 } ])
  expect(equals(toCompareSame, testSet)).toBeTruthy()
  expect(equals(toCompareDifferent, testSet)).toBeFalsy()
  expect(equalsRamda(toCompareSame, testSet)).toBeTruthy()
  expect(equalsRamda(toCompareDifferent, testSet)).toBeFalsy()
})

test('compare simple sets', () => {
  const testSet = new Set([ '2', '3', '3', '2', '1' ])
  expect(equals(new Set([ '3', '2', '1' ]), testSet)).toBeTruthy()
  expect(equals(new Set([ '3', '2', '0' ]), testSet)).toBeFalsy()
})

test('various examples', () => {
  expect(equals([ 1, 2, 3 ])([ 1, 2, 3 ])).toBeTrue()

  expect(equals([ 1, 2, 3 ], [ 1, 2 ])).toBeFalse()

  expect(equals(1, 1)).toBeTrue()

  expect(equals(1, '1')).toBeFalse()

  expect(equals({}, {})).toBeTrue()

  expect(equals({
    a : 1,
    b : 2,
  },
  {
    a : 1,
    b : 2,
  })).toBeTrue()

  expect(equals({
    a : 1,
    b : 2,
  },
  {
    a : 1,
    b : 1,
  })).toBeFalse()

  expect(equals({
    a : 1,
    b : false,
  },
  {
    a : 1,
    b : 1,
  })).toBeFalse()

  expect(equals({
    a : 1,
    b : 2,
  },
  {
    a : 1,
    b : 2,
    c : 3,
  })).toBeFalse()

  expect(equals({
    x : {
      a : 1,
      b : 2,
    },
  },
  {
    x : {
      a : 1,
      b : 2,
      c : 3,
    },
  })).toBeFalse()

  expect(equals({
    a : 1,
    b : 2,
  },
  {
    a : 1,
    b : 3,
  })).toBeFalse()

  expect(equals({ a : { b : { c : 1 } } }, { a : { b : { c : 1 } } })).toBeTrue()

  expect(equals({ a : { b : { c : 1 } } }, { a : { b : { c : 2 } } })).toBeFalse()

  expect(equals({ a : {} }, { a : {} })).toBeTrue()

  expect(equals('', '')).toBeTrue()

  expect(equals('foo', 'foo')).toBeTrue()

  expect(equals('foo', 'bar')).toBeFalse()

  expect(equals(0, false)).toBeFalse()

  expect(equals(/\s/g, null)).toBeFalse()

  expect(equals(null, null)).toBeTrue()

  expect(equals(false)(null)).toBeFalse()
})

test('with custom functions', () => {
  function foo(){
    return 1
  }
  foo.prototype.toString = () => ''
  const result = equals(foo, foo)

  expect(result).toBeTrue()
})

test('with classes', () => {
  class Foo{}
  const foo = new Foo()
  const result = equals(foo, foo)

  expect(result).toBeTrue()
})

test('with negative zero', () => {
  expect(equals(-0, -0)).toBeTrue()
  expect(equals(-0, 0)).toBeFalse()
  expect(equals(0, 0)).toBeTrue()
  expect(equals(-0, 1)).toBeFalse()
})

test('with big int', () => {
  const a = BigInt(9007199254740991)
  const b = BigInt(9007199254740991)
  const c = BigInt(7007199254740991)
  expect(equals(a, b)).toBeTrue()
  expect(equals(a, c)).toBeFalse()
})

describe('brute force', () => {
  compareCombinations({
    callback : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
{
  "ERRORS_MESSAGE_MISMATCH": 0,
  "ERRORS_TYPE_MISMATCH": 0,
  "RESULTS_MISMATCH": 0,
  "SHOULD_NOT_THROW": 0,
  "SHOULD_THROW": 0,
  "TOTAL_TESTS": 289,
}
`)
    },
    firstInput  : variousTypes,
    fn          : equals,
    fnRamda     : equalsRamda,
    secondInput : variousTypes,
  })
})

import {equals} from 'rambda'

describe('R.equals', () => {
  it('happy', () => {
    const result = equals(4, 1)
    result // $ExpectType boolean
  })
  it('with object', () => {
    const foo = {a: 1}
    const bar = {a: 2}
    const result = equals(foo, bar)
    result // $ExpectType boolean
  })
  it('curried', () => {
    const result = equals(4)(1)

    result // $ExpectType boolean
  })
})

evolve

evolve<T, U>(rules: ((x: T) => U)[], list: T[]): U[]

It takes object or array of functions as set of rules. These rules are applied to the iterable input to produce the result.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20rules%20%3D%20%7B%0A%20%20foo%20%3A%20add(1)%2C%0A%20%20bar%20%3A%20add(-1)%2C%0A%7D%0Aconst%20input%20%3D%20%7B%0A%20%20a%20%20%20%3A%201%2C%0A%20%20foo%20%3A%202%2C%0A%20%20bar%20%3A%203%2C%0A%7D%0Aconst%20result%20%3D%20evolve(rules%2C%20input)%0Aconst%20expected%20%3D%20%7B%0A%20%20a%20%20%20%3A%201%2C%0A%20%20foo%20%3A%203%2C%0A%20%20bar%20%3A%202%2C%0A%7D)%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.evolve</strong> example in Rambda REPL</a>

evolve<T, U>(rules: ((x: T) => U)[], list: T[]): U[];
evolve<T, U>(rules: ((x: T) => U)[]) : (list: T[]) => U[];
evolve<E extends Evolver, V extends Evolvable<E>>(rules: E, obj: V): Evolve<V, E>;
evolve<E extends Evolver>(rules: E): <V extends Evolvable<E>>(obj: V) => Evolve<V, E>;

import { isArray } from './_internals/isArray.js'
import { mapArray, mapObject } from './map.js'
import { type } from './type.js'

export function evolveArray(rules, list){
  return mapArray(
    (x, i) => {
      if (type(rules[ i ]) === 'Function'){
        return rules[ i ](x)
      }

      return x
    },
    list,
    true
  )
}

export function evolveObject(rules, iterable){
  return mapObject((x, prop) => {
    if (type(x) === 'Object'){
      const typeRule = type(rules[ prop ])
      if (typeRule === 'Function'){
        return rules[ prop ](x)
      }
      if (typeRule === 'Object'){
        return evolve(rules[ prop ], x)
      }

      return x
    }
    if (type(rules[ prop ]) === 'Function'){
      return rules[ prop ](x)
    }

    return x
  }, iterable)
}

export function evolve(rules, iterable){
  if (arguments.length === 1){
    return _iterable => evolve(rules, _iterable)
  }
  const rulesType = type(rules)
  const iterableType = type(iterable)

  if (iterableType !== rulesType){
    throw new Error('iterableType !== rulesType')
  }

  if (![ 'Object', 'Array' ].includes(rulesType)){
    throw new Error(`'iterable' and 'rules' are from wrong type ${ rulesType }`)
  }

  if (iterableType === 'Object'){
    return evolveObject(rules, iterable)
  }

  return evolveArray(rules, iterable)
}

import { evolve as evolveRamda } from 'ramda'

import { add } from '../rambda.js'
import { compareCombinations, compareToRamda } from './_internals/testUtils.js'
import { evolve } from './evolve.js'

test('happy', () => {
  const rules = {
    foo    : add(1),
    nested : { bar : x => Object.keys(x).length },
  }
  const input = {
    a      : 1,
    foo    : 2,
    nested : { bar : { z : 3 } },
  }
  const result = evolve(rules, input)
  expect(result).toEqual({
    a      : 1,
    foo    : 3,
    nested : { bar : 1 },
  })
})

test('nested rule is wrong', () => {
  const rules = {
    foo    : add(1),
    nested : { bar : 10 },
  }
  const input = {
    a      : 1,
    foo    : 2,
    nested : { bar : { z : 3 } },
  }
  const result = evolve(rules)(input)
  expect(result).toEqual({
    a      : 1,
    foo    : 3,
    nested : { bar : { z : 3 } },
  })
})

test('is recursive', () => {
  const rules = {
    nested : {
      second : add(-1),
      third  : add(1),
    },
  }
  const object = {
    first  : 1,
    nested : {
      second : 2,
      third  : 3,
    },
  }
  const expected = {
    first  : 1,
    nested : {
      second : 1,
      third  : 4,
    },
  }
  const result = evolve(rules, object)
  expect(result).toEqual(expected)
})

test('ignores primitive values', () => {
  const rules = {
    n : 2,
    m : 'foo',
  }
  const object = {
    n : 0,
    m : 1,
  }
  const expected = {
    n : 0,
    m : 1,
  }
  const result = evolve(rules, object)
  expect(result).toEqual(expected)
})

test('with array', () => {
  const rules = [ add(1), add(-1) ]
  const list = [ 100, 1400 ]
  const expected = [ 101, 1399 ]
  const result = evolve(rules, list)
  expect(result).toEqual(expected)
})

const rulesObject = { a : add(1) }
const rulesList = [ add(1) ]
const possibleIterables = [ null, undefined, '', 42, [], [ 1 ], { a : 1 } ]
const possibleRules = [ ...possibleIterables, rulesList, rulesObject ]

describe('brute force', () => {
  compareCombinations({
    firstInput : possibleRules,
    callback   : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
        {
          "ERRORS_MESSAGE_MISMATCH": 0,
          "ERRORS_TYPE_MISMATCH": 4,
          "RESULTS_MISMATCH": 0,
          "SHOULD_NOT_THROW": 51,
          "SHOULD_THROW": 0,
          "TOTAL_TESTS": 63,
        }
      `)
    },
    secondInput : possibleIterables,
    fn          : evolve,
    fnRamda     : evolveRamda,
  })
})

import {evolve, add} from 'rambda'

describe('R.evolve', () => {
  it('happy', () => {
    const input = {
      foo: 2,
      nested: {
        a: 1,
        bar: 3,
      },
    }
    const rules = {
      foo: add(1),
      nested: {
        a: add(-1),
        bar: add(1),
      },
    }
    const result = evolve(rules, input)
    const curriedResult = evolve(rules)(input)

    result.nested.a // $ExpectType number
    curriedResult.nested.a // $ExpectType number
    result.nested.bar // $ExpectType number
    result.foo // $ExpectType number
  })
  it('with array', () => {
    const rules = [String, String]
    const input = [100, 1400]
    const result = evolve(rules, input)
    const curriedResult = evolve(rules)(input)
    result // $ExpectType string[]
    curriedResult // $ExpectType string[]
  })
})

F

F(): boolean

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20F()%20%2F%2F%20%3D%3E%20false">Try this <strong>R.F</strong> example in Rambda REPL</a>

F(): boolean;

export function F(){
  return false
}

filter

filter<T>(predicate: Predicate<T>): (input: T[]) => T[]

It filters list or object input using a predicate function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B3%2C%204%2C%203%2C%202%5D%0Aconst%20listPredicate%20%3D%20x%20%3D%3E%20x%20%3E%202%0A%0Aconst%20object%20%3D%20%7Babc%3A%20'fo'%2C%20xyz%3A%20'bar'%2C%20baz%3A%20'foo'%7D%0Aconst%20objectPredicate%20%3D%20(x%2C%20prop)%20%3D%3E%20x.length%20%2B%20prop.length%20%3E%205%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.filter(listPredicate%2C%20list)%2C%0A%20%20R.filter(objectPredicate%2C%20object)%0A%5D%0A%2F%2F%20%3D%3E%20%5B%20%5B3%2C%204%5D%2C%20%7B%20xyz%3A%20'bar'%2C%20baz%3A%20'foo'%7D%20%5D">Try this <strong>R.filter</strong> example in Rambda REPL</a>

filter<T>(predicate: Predicate<T>): (input: T[]) => T[];
filter<T>(predicate: Predicate<T>, input: T[]): T[];
filter<T, U>(predicate: ObjectPredicate<T>): (x: Dictionary<T>) => Dictionary<T>;
filter<T>(predicate: ObjectPredicate<T>, x: Dictionary<T>): Dictionary<T>;

import { isArray } from './_internals/isArray.js'

export function filterObject(predicate, obj){
  const willReturn = {}

  for (const prop in obj){
    if (predicate(
      obj[ prop ], prop, obj
    )){
      willReturn[ prop ] = obj[ prop ]
    }
  }

  return willReturn
}

export function filterArray(
  predicate, list, indexed = false
){
  let index = 0
  const len = list.length
  const willReturn = []

  while (index < len){
    const predicateResult = indexed ?
      predicate(list[ index ], index) :
      predicate(list[ index ])
    if (predicateResult){
      willReturn.push(list[ index ])
    }

    index++
  }

  return willReturn
}

export function filter(predicate, iterable){
  if (arguments.length === 1)
    return _iterable => filter(predicate, _iterable)
  if (!iterable){
    throw new Error('Incorrect iterable input')
  }

  if (isArray(iterable)) return filterArray(
    predicate, iterable, false
  )

  return filterObject(predicate, iterable)
}

import { filter as filterRamda } from 'ramda'

import { filter } from './filter.js'
import { T } from './T.js'

const sampleObject = {
  a : 1,
  b : 2,
  c : 3,
  d : 4,
}

test('happy', () => {
  const isEven = n => n % 2 === 0

  expect(filter(isEven, [ 1, 2, 3, 4 ])).toEqual([ 2, 4 ])
  expect(filter(isEven, {
    a : 1,
    b : 2,
    d : 3,
  })).toEqual({ b : 2 })
})

test('predicate when input is object', () => {
  const obj = {
    a : 1,
    b : 2,
  }
  const predicate = (
    val, prop, inputObject
  ) => {
    expect(inputObject).toEqual(obj)
    expect(typeof prop).toBe('string')

    return val < 2
  }
  expect(filter(predicate, obj)).toEqual({ a : 1 })
})

test('with object', () => {
  const isEven = n => n % 2 === 0
  const result = filter(isEven, sampleObject)
  const expectedResult = {
    b : 2,
    d : 4,
  }

  expect(result).toEqual(expectedResult)
})

test('bad inputs difference between Ramda and Rambda', () => {
  expect(() => filter(T, null)).toThrowWithMessage(Error,
    'Incorrect iterable input')
  expect(() => filter(T)(undefined)).toThrowWithMessage(Error,
    'Incorrect iterable input')
  expect(() => filterRamda(T, null)).toThrowWithMessage(TypeError,
    'Cannot read properties of null (reading \'fantasy-land/filter\')')
  expect(() => filterRamda(T, undefined)).toThrowWithMessage(TypeError,
    'Cannot read properties of undefined (reading \'fantasy-land/filter\')')
})

import {filter} from 'rambda'

const list = [1, 2, 3]
const obj = {a: 1, b: 2}

describe('R.filter with array', () => {
  it('happy', () => {
    const result = filter<number>(x => {
      x // $ExpectType number
      return x > 1
    }, list)
    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = filter<number>(x => {
      x // $ExpectType number
      return x > 1
    })(list)
    result // $ExpectType number[]
  })
})

describe('R.filter with objects', () => {
  it('happy', () => {
    const result = filter<number>((val, prop, origin) => {
      val // $ExpectType number
      prop // $ExpectType string
      origin // $ExpectType Dictionary<number>

      return val > 1
    }, obj)
    result // $ExpectType Dictionary<number>
  })
  it('curried version requires second dummy type', () => {
    const result = filter<number, any>((val, prop, origin) => {
      val // $ExpectType number
      prop // $ExpectType string
      origin // $ExpectType Dictionary<number>

      return val > 1
    })(obj)
    result // $ExpectType Dictionary<number>
  })
})

find

find<T>(predicate: (x: T) => boolean, list: T[]): T | undefined

It returns the first element of list that satisfy the predicate.

If there is no such element, it returns undefined.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20predicate%20%3D%20x%20%3D%3E%20R.type(x.foo)%20%3D%3D%3D%20'Number'%0Aconst%20list%20%3D%20%5B%7Bfoo%3A%20'bar'%7D%2C%20%7Bfoo%3A%201%7D%5D%0A%0Aconst%20result%20%3D%20R.find(predicate%2C%20list)%0A%2F%2F%20%3D%3E%20%7Bfoo%3A%201%7D">Try this <strong>R.find</strong> example in Rambda REPL</a>

find<T>(predicate: (x: T) => boolean, list: T[]): T | undefined;
find<T>(predicate: (x: T) => boolean): (list: T[]) => T | undefined;

export function find(predicate, list){
  if (arguments.length === 1) return _list => find(predicate, _list)

  let index = 0
  const len = list.length

  while (index < len){
    const x = list[ index ]
    if (predicate(x)){
      return x
    }

    index++
  }
}

import { find } from './find.js'
import { propEq } from './propEq.js'

const list = [ { a : 1 }, { a : 2 }, { a : 3 } ]

test('happy', () => {
  const fn = propEq(2, 'a')
  expect(find(fn, list)).toEqual({ a : 2 })
})

test('with curry', () => {
  const fn = propEq(4, 'a')
  expect(find(fn)(list)).toBeUndefined()
})

test('with empty list', () => {
  expect(find(() => true, [])).toBeUndefined()
})

import {find} from 'rambda'

const list = [1, 2, 3]

describe('R.find', () => {
  it('happy', () => {
    const predicate = (x: number) => x > 2
    const result = find(predicate, list)
    result // $ExpectType number | undefined
  })
  it('curried', () => {
    const predicate = (x: number) => x > 2
    const result = find(predicate)(list)
    result // $ExpectType number | undefined
  })
})

findIndex

findIndex<T>(predicate: (x: T) => boolean, list: T[]): number

It returns the index of the first element of list satisfying the predicate function.

If there is no such element, then -1 is returned.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20predicate%20%3D%20x%20%3D%3E%20R.type(x.foo)%20%3D%3D%3D%20'Number'%0Aconst%20list%20%3D%20%5B%7Bfoo%3A%20'bar'%7D%2C%20%7Bfoo%3A%201%7D%5D%0A%0Aconst%20result%20%3D%20R.findIndex(predicate%2C%20list)%0A%2F%2F%20%3D%3E%201">Try this <strong>R.findIndex</strong> example in Rambda REPL</a>

findIndex<T>(predicate: (x: T) => boolean, list: T[]): number;
findIndex<T>(predicate: (x: T) => boolean): (list: T[]) => number;

export function findIndex(predicate, list){
  if (arguments.length === 1) return _list => findIndex(predicate, _list)

  const len = list.length
  let index = -1

  while (++index < len){
    if (predicate(list[ index ])){
      return index
    }
  }

  return -1
}

import { findIndex } from './findIndex.js'
import { propEq } from './propEq.js'

const list = [ { a : 1 }, { a : 2 }, { a : 3 } ]

test('happy', () => {
  expect(findIndex(propEq(2, 'a'), list)).toBe(1)
  expect(findIndex(propEq(1, 'a'))(list)).toBe(0)
  expect(findIndex(propEq(4, 'a'))(list)).toBe(-1)
})

import {findIndex} from 'rambda'

const list = [1, 2, 3]

describe('R.findIndex', () => {
  it('happy', () => {
    const predicate = (x: number) => x > 2
    const result = findIndex(predicate, list)
    result // $ExpectType number
  })
  it('curried', () => {
    const predicate = (x: number) => x > 2
    const result = findIndex(predicate)(list)
    result // $ExpectType number
  })
})

findLast

findLast<T>(fn: (x: T) => boolean, list: T[]): T | undefined

It returns the last element of list satisfying the predicate function.

If there is no such element, then undefined is returned.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20predicate%20%3D%20x%20%3D%3E%20R.type(x.foo)%20%3D%3D%3D%20'Number'%0Aconst%20list%20%3D%20%5B%7Bfoo%3A%200%7D%2C%20%7Bfoo%3A%201%7D%5D%0A%0Aconst%20result%20%3D%20R.findLast(predicate%2C%20list)%0A%2F%2F%20%3D%3E%20%7Bfoo%3A%201%7D">Try this <strong>R.findLast</strong> example in Rambda REPL</a>

findLast<T>(fn: (x: T) => boolean, list: T[]): T | undefined;
findLast<T>(fn: (x: T) => boolean): (list: T[]) => T | undefined;

export function findLast(predicate, list){
  if (arguments.length === 1) return _list => findLast(predicate, _list)

  let index = list.length

  while (--index >= 0){
    if (predicate(list[ index ])){
      return list[ index ]
    }
  }

  return undefined
}

import { findLast } from './findLast.js'

test('happy', () => {
  const result = findLast(x => x > 1, [ 1, 1, 1, 2, 3, 4, 1 ])
  expect(result).toBe(4)

  expect(findLast(x => x === 0, [ 0, 1, 1, 2, 3, 4, 1 ])).toBe(0)
})

test('with curry', () => {
  expect(findLast(x => x > 1)([ 1, 1, 1, 2, 3, 4, 1 ])).toBe(4)
})

const obj1 = { x : 100 }
const obj2 = { x : 200 }
const a = [ 11, 10, 9, 'cow', obj1, 8, 7, 100, 200, 300, obj2, 4, 3, 2, 1, 0 ]
const even = function (x){
  return x % 2 === 0
}
const gt100 = function (x){
  return x > 100
}
const isStr = function (x){
  return typeof x === 'string'
}
const xGt100 = function (o){
  return o && o.x > 100
}

test('ramda 1', () => {
  expect(findLast(even, a)).toBe(0)
  expect(findLast(gt100, a)).toBe(300)
  expect(findLast(isStr, a)).toBe('cow')
  expect(findLast(xGt100, a)).toEqual(obj2)
})

test('ramda 2', () => {
  expect(findLast(even, [ 'zing' ])).toBeUndefined()
})

test('ramda 3', () => {
  expect(findLast(even, [ 2, 3, 5 ])).toBe(2)
})

test('ramda 4', () => {
  expect(findLast(even, [])).toBeUndefined()
})

import {findLast} from 'rambda'

const list = [1, 2, 3]

describe('R.findLast', () => {
  it('happy', () => {
    const predicate = (x: number) => x > 2
    const result = findLast(predicate, list)
    result // $ExpectType number | undefined
  })
  it('curried', () => {
    const predicate = (x: number) => x > 2
    const result = findLast(predicate)(list)
    result // $ExpectType number | undefined
  })
})

findLastIndex

findLastIndex<T>(predicate: (x: T) => boolean, list: T[]): number

It returns the index of the last element of list satisfying the predicate function.

If there is no such element, then -1 is returned.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20predicate%20%3D%20x%20%3D%3E%20R.type(x.foo)%20%3D%3D%3D%20'Number'%0Aconst%20list%20%3D%20%5B%7Bfoo%3A%200%7D%2C%20%7Bfoo%3A%201%7D%5D%0A%0Aconst%20result%20%3D%20R.findLastIndex(predicate%2C%20list)%0A%2F%2F%20%3D%3E%201">Try this <strong>R.findLastIndex</strong> example in Rambda REPL</a>

findLastIndex<T>(predicate: (x: T) => boolean, list: T[]): number;
findLastIndex<T>(predicate: (x: T) => boolean): (list: T[]) => number;

export function findLastIndex(fn, list){
  if (arguments.length === 1) return _list => findLastIndex(fn, _list)

  let index = list.length

  while (--index >= 0){
    if (fn(list[ index ])){
      return index
    }
  }

  return -1
}

import { findLastIndex } from './findLastIndex.js'

test('happy', () => {
  const result = findLastIndex(x => x > 1, [ 1, 1, 1, 2, 3, 4, 1 ])

  expect(result).toBe(5)

  expect(findLastIndex(x => x === 0, [ 0, 1, 1, 2, 3, 4, 1 ])).toBe(0)
})

test('with curry', () => {
  expect(findLastIndex(x => x > 1)([ 1, 1, 1, 2, 3, 4, 1 ])).toBe(5)
})

const obj1 = { x : 100 }
const obj2 = { x : 200 }
const a = [ 11, 10, 9, 'cow', obj1, 8, 7, 100, 200, 300, obj2, 4, 3, 2, 1, 0 ]
const even = function (x){
  return x % 2 === 0
}
const gt100 = function (x){
  return x > 100
}
const isStr = function (x){
  return typeof x === 'string'
}
const xGt100 = function (o){
  return o && o.x > 100
}

test('ramda 1', () => {
  expect(findLastIndex(even, a)).toBe(15)
  expect(findLastIndex(gt100, a)).toBe(9)
  expect(findLastIndex(isStr, a)).toBe(3)
  expect(findLastIndex(xGt100, a)).toBe(10)
})

test('ramda 2', () => {
  expect(findLastIndex(even, [ 'zing' ])).toBe(-1)
})

test('ramda 3', () => {
  expect(findLastIndex(even, [ 2, 3, 5 ])).toBe(0)
})

test('ramda 4', () => {
  expect(findLastIndex(even, [])).toBe(-1)
})

import {findLastIndex} from 'rambda'

const list = [1, 2, 3]

describe('R.findLastIndex', () => {
  it('happy', () => {
    const predicate = (x: number) => x > 2
    const result = findLastIndex(predicate, list)
    result // $ExpectType number
  })
  it('curried', () => {
    const predicate = (x: number) => x > 2
    const result = findLastIndex(predicate)(list)
    result // $ExpectType number
  })
})

flatten

flatten<T>(list: any[]): T[]

It deeply flattens an array.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.flatten(%5B%0A%20%201%2C%20%0A%20%202%2C%20%0A%20%20%5B3%2C%2030%2C%20%5B300%5D%5D%2C%20%0A%20%20%5B4%5D%0A%5D)%0A%2F%2F%20%3D%3E%20%5B%201%2C%202%2C%203%2C%2030%2C%20300%2C%204%20%5D">Try this <strong>R.flatten</strong> example in Rambda REPL</a>

flatten<T>(list: any[]): T[];

import { isArray } from './_internals/isArray.js'

export function flatten(list, input){
  const willReturn = input === undefined ? [] : input

  for (let i = 0; i < list.length; i++){
    if (isArray(list[ i ])){
      flatten(list[ i ], willReturn)
    } else {
      willReturn.push(list[ i ])
    }
  }

  return willReturn
}

import { flatten } from './flatten.js'

test('happy', () => {
  expect(flatten([ 1, 2, 3, [ [ [ [ [ 4 ] ] ] ] ] ])).toEqual([ 1, 2, 3, 4 ])

  expect(flatten([ 1, [ 2, [ [ 3 ] ] ], [ 4 ] ])).toEqual([ 1, 2, 3, 4 ])

  expect(flatten([ 1, [ 2, [ [ [ 3 ] ] ] ], [ 4 ] ])).toEqual([ 1, 2, 3, 4 ])

  expect(flatten([ 1, 2, [ 3, 4 ], 5, [ 6, [ 7, 8, [ 9, [ 10, 11 ], 12 ] ] ] ])).toEqual([ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ])
})

test('readme example', () => {
  const result = flatten([ 1, 2, [ 3, 30, [ 300 ] ], [ 4 ] ])
  expect(result).toEqual([ 1, 2, 3, 30, 300, 4 ])
})

import {flatten} from 'rambda'

describe('flatten', () => {
  it('happy', () => {
    const result = flatten<number>([1, 2, [3, [4]]])
    result // $ExpectType number[]
  })
})

flip

It returns function which calls fn with exchanged first and second argument.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20subtractFlip%20%3D%20R.flip(R.subtract)%0A%0Aconst%20result%20%3D%20%5B%0A%20%20subtractFlip(1%2C7)%2C%0A%20%20R.subtract(1%2C%206)%0A%5D%20%20%0A%2F%2F%20%3D%3E%20%5B6%2C%20-6%5D">Try this <strong>R.flip</strong> example in Rambda REPL</a>

forEach

forEach<T>(fn: Iterator<T, void>, list: T[]): T[]

It applies iterable function over all members of list and returns list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20sideEffect%20%3D%20%7B%7D%0Aconst%20result%20%3D%20R.forEach(%0A%20%20x%20%3D%3E%20sideEffect%5B%60foo%24%7Bx%7D%60%5D%20%3D%20x%0A)(%5B1%2C%202%5D)%0A%0AsideEffect%20%2F%2F%20%3D%3E%20%7Bfoo1%3A%201%2C%20foo2%3A%202%7D%0Aresult%20%2F%2F%20%3D%3E%20%5B1%2C%202%5D">Try this <strong>R.forEach</strong> example in Rambda REPL</a>

forEach<T>(fn: Iterator<T, void>, list: T[]): T[];
forEach<T>(fn: Iterator<T, void>): (list: T[]) => T[];
forEach<T>(fn: ObjectIterator<T, void>, list: Dictionary<T>): Dictionary<T>;
forEach<T, U>(fn: ObjectIterator<T, void>): (list: Dictionary<T>) => Dictionary<T>;

import { isArray } from './_internals/isArray.js'
import { forEachObjIndexedFn } from './forEachObjIndexed.js'

export function forEach(fn, iterable){
  if (arguments.length === 1) return _list => forEach(fn, _list)
  if (iterable === undefined) return

  if (isArray(iterable)){
    let index = 0
    const len = iterable.length

    while (index < len){
      fn(iterable[ index ])
      index++
    }
  } else return forEachObjIndexedFn(fn, iterable)

  return iterable
}

import { forEach } from './forEach.js'
import { type } from './type.js'

test('happy', () => {
  const sideEffect = {}
  forEach(x => sideEffect[ `foo${ x }` ] = x + 10)([ 1, 2 ])

  expect(sideEffect).toEqual({
    foo1 : 11,
    foo2 : 12,
  })
})

test('iterate over object', () => {
  const obj = {
    a : 1,
    b : [ 1, 2 ],
    c : { d : 7 },
    f : 'foo',
  }
  const result = {}
  const returned = forEach((
    val, prop, inputObj
  ) => {
    expect(type(inputObj)).toBe('Object')
    result[ prop ] = `${ prop }-${ type(val) }`
  })(obj)

  const expected = {
    a : 'a-Number',
    b : 'b-Array',
    c : 'c-Object',
    f : 'f-String',
  }

  expect(result).toEqual(expected)
  expect(returned).toEqual(obj)
})

test('with empty list', () => {
  const list = []
  const result = forEach(x => x * x)(list)

  expect(result).toEqual(list)
})

test('with wrong input', () => {
  const list = undefined
  const result = forEach(x => x * x)(list)

  expect(result).toBeUndefined()
})

test('returns the input', () => {
  const list = [ 1, 2, 3 ]
  const result = forEach(x => x * x)(list)

  expect(result).toEqual(list)
})

import {forEach} from 'rambda'

const list = [1, 2, 3]
const obj = {a: 1, b: 2}

describe('R.forEach with arrays', () => {
  it('happy', () => {
    const result = forEach(a => {
      a // $ExpectType number
    }, list)
    result // $ExpectType number[]
  })
  it('curried require an explicit typing', () => {
    const result = forEach<number>(a => {
      a // $ExpectType number
    })(list)
    result // $ExpectType number[]
  })
})

describe('R.forEach with objects', () => {
  it('happy', () => {
    const result = forEach((a, b, c) => {
      a // $ExpectType number
      b // $ExpectType string
      c // $ExpectType Dictionary<number>
      return `${a}`
    }, obj)
    result // $ExpectType Dictionary<number>
  })
  it('curried require an input typing and a dummy third typing', () => {
    // Required in order all typings to work
    const result = forEach<number, any>((a, b, c) => {
      a // $ExpectType number
      b // $ExpectType string
      c // $ExpectType Dictionary<number>
    })(obj)
    result // $ExpectType Dictionary<number>
  })
  it('iterator without property', () => {
    const result = forEach(a => {
      a // $ExpectType number
    }, obj)
    result // $ExpectType Dictionary<number>
  })
})

forEachObjIndexed

fromPairs

It transforms a listOfPairs to an object.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20listOfPairs%20%3D%20%5B%20%5B%20'a'%2C%201%20%5D%2C%20%5B%20'b'%2C%202%20%5D%2C%20%5B%20'c'%2C%20%5B%203%2C%204%20%5D%20%5D%20%5D%0Aconst%20expected%20%3D%20%7B%0A%20%20a%20%3A%201%2C%0A%20%20b%20%3A%202%2C%0A%20%20c%20%3A%20%5B%203%2C%204%20%5D%2C%0A%7D%0A%0Aconst%20result%20%3D%20R.fromPairs(listOfPairs)%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.fromPairs</strong> example in Rambda REPL</a>

groupBy

It splits list according to a provided groupFn function and returns an object.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%20'a'%2C%20'b'%2C%20'aa'%2C%20'bb'%20%5D%0Aconst%20groupFn%20%3D%20x%20%3D%3E%20x.length%0A%0Aconst%20result%20%3D%20R.groupBy(groupFn%2C%20list)%0A%2F%2F%20%3D%3E%20%7B%20'1'%3A%20%5B'a'%2C%20'b'%5D%2C%20'2'%3A%20%5B'aa'%2C%20'bb'%5D%20%7D">Try this <strong>R.groupBy</strong> example in Rambda REPL</a>

groupWith

It returns separated version of list or string input, where separation is done with equality compareFn function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20isConsecutive%20%3D%20(x%2C%20y)%20%3D%3E%20x%20%3D%3D%3D%20y%0Aconst%20list%20%3D%20%5B1%2C%202%2C%202%2C%201%2C%201%2C%202%5D%0A%0Aconst%20result%20%3D%20R.groupWith(isConsecutive%2C%20list)%0A%2F%2F%20%3D%3E%20%5B%5B1%5D%2C%20%5B2%2C2%5D%2C%20%5B1%2C1%5D%2C%20%5B2%5D%5D">Try this <strong>R.groupWith</strong> example in Rambda REPL</a>

gt

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5BR.gt(2%2C%201)%2C%20R.gt(2%2C%203)%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.gt</strong> example in Rambda REPL</a>

gte

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5BR.gte(2%2C%201)%2C%20R.gte(2%2C%202)%2C%20R.gte(2%2C%203)%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%2C%20false%5D">Try this <strong>R.gte</strong> example in Rambda REPL</a>

has

has<T>(prop: string, obj: T): boolean

It returns true if obj has property prop.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A%201%7D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.has('a'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.has('b'%2C%20Record%3Cstring%2C%20unknown%3E)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.has</strong> example in Rambda REPL</a>

has<T>(prop: string, obj: T): boolean;
has(prop: string): <T>(obj: T) => boolean;

export function has(prop, obj){
  if (arguments.length === 1) return _obj => has(prop, _obj)

  if (!obj) return false

  return obj.hasOwnProperty(prop)
}

import { has } from './has.js'

test('happy', () => {
  expect(has('a')({ a : 1 })).toBeTrue()
  expect(has('b', { a : 1 })).toBeFalse()
})

test('with non-object', () => {
  expect(has('a', undefined)).toBeFalse()
  expect(has('a', null)).toBeFalse()
  expect(has('a', true)).toBeFalse()
  expect(has('a', '')).toBeFalse()
  expect(has('a', /a/)).toBeFalse()
})

import {has} from 'rambda'

describe('R.has', () => {
  it('happy', () => {
    const result = has('foo', {a: 1})
    const curriedResult = has('bar')({a: 1})
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
})

hasIn

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.hasIn('a'%2C%20%7Ba%3A%201%7D)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.hasIn</strong> example in Rambda REPL</a>

hasPath

hasPath<T>(
  path: string | string[],
  input: object
): boolean

It will return true, if input object has truthy path(calculated with R.path).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20path%20%3D%20'a.b'%0Aconst%20pathAsArray%20%3D%20%5B'a'%2C%20'b'%5D%0Aconst%20obj%20%3D%20%7Ba%3A%20%7Bb%3A%20%5B%5D%7D%7D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.hasPath(path%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.hasPath(pathAsArray%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.hasPath('a.c'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%2C%20false%5D">Try this <strong>R.hasPath</strong> example in Rambda REPL</a>

hasPath<T>(
  path: string | string[],
  input: object
): boolean;
hasPath<T>(
  path: string | string[]
): (input: object) => boolean;

import { path } from './path.js'

export function hasPath(pathInput, obj){
  if (arguments.length === 1){
    return objHolder => hasPath(pathInput, objHolder)
  }

  return path(pathInput, obj) !== undefined
}

import { hasPath } from './hasPath.js'

test('when true', () => {
  const path = 'a.b'
  const obj = { a : { b : [] } }

  const result = hasPath(path)(obj)
  const expectedResult = true

  expect(result).toEqual(expectedResult)
})

test('when false', () => {
  const path = 'a.b'
  const obj = {}

  const result = hasPath(path, obj)
  const expectedResult = false

  expect(result).toEqual(expectedResult)
})

import {hasPath} from 'rambda'

describe('R.hasPath', () => {
  it('string path', () => {
    const obj = {a: {b: 1}}
    const result = hasPath('a.b', obj)
    const curriedResult = hasPath('a.c')(obj)
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
  it('array path', () => {
    const obj = {a: {b: 1}}
    const result = hasPath(['a', 'b'], obj)
    const curriedResult = hasPath(['a', 'c'])(obj)
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
})

head

head(str: string): string

It returns the first element of list or string input. It returns undefined if array has length of 0.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.head(%5B1%2C%202%2C%203%5D)%2C%0A%20%20R.head('foo')%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B1%2C%20'f'%5D">Try this <strong>R.head</strong> example in Rambda REPL</a>

head(str: string): string;
head(str: ''): undefined;
head(list: readonly[]): undefined;
head<T>(list: never[]): undefined;
head<T extends unknown[]>(array: T): FirstArrayElement<T>
head<T extends readonly unknown[]>(array: T): FirstArrayElement<T>

export function head(listOrString){
  if (typeof listOrString === 'string') return listOrString[ 0 ] || ''

  return listOrString[ 0 ]
}

import { head } from './head.js'

test('head', () => {
  expect(head([ 'fi', 'fo', 'fum' ])).toBe('fi')
  expect(head([])).toBeUndefined()
  expect(head('foo')).toBe('f')
  expect(head('')).toBe('')
})

import {
  emptyList,
  emptyString,
  mixedList,
  mixedListConst,
  numberList,
  numberListConst,
  string,
} from '_internals/typescriptTestUtils'
import {head, last} from 'rambda'

describe('R.head', () => {
  it('string', () => {
    head(string) // $ExpectType string
    last(string) // $ExpectType string
  })
  it('empty string', () => {
    head(emptyString) // $ExpectType undefined
    last(emptyString) // $ExpectType undefined
  })
  it('array', () => {
    head(numberList) // $ExpectType number
    head(numberListConst) // $ExpectType 1

    last(numberList) // $ExpectType number
    last(numberListConst) // $ExpectType 3
  })
  it('empty array', () => {
    const list = [] as const
    head(emptyList) // $ExpectType undefined
    head(list) // $ExpectType undefined
    last(emptyList) // $ExpectType undefined
    last(list) // $ExpectType undefined
  })

  it('mixed', () => {
    head(mixedList) // $ExpectType string | number
    head(mixedListConst) // $ExpectType 1
    last(mixedList) // $ExpectType string | number
    last(mixedListConst) // $ExpectType "bar"
  })
})

identical

It returns true if its arguments a and b are identical.

Otherwise, it returns false.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20objA%20%3D%20%7Ba%3A%201%7D%3B%0Aconst%20objB%20%3D%20%7Ba%3A%201%7D%3B%0AR.identical(objA%2C%20objA)%3B%20%2F%2F%20%3D%3E%20true%0AR.identical(objA%2C%20objB)%3B%20%2F%2F%20%3D%3E%20false%0AR.identical(1%2C%201)%3B%20%2F%2F%20%3D%3E%20true%0AR.identical(1%2C%20'1')%3B%20%2F%2F%20%3D%3E%20false%0AR.identical(%5B%5D%2C%20%5B%5D)%3B%20%2F%2F%20%3D%3E%20false%0AR.identical(0%2C%20-0)%3B%20%2F%2F%20%3D%3E%20false%0Aconst%20result%20%3D%20R.identical(NaN%2C%20NaN)%3B%20%2F%2F%20%3D%3E%20true">Try this <strong>R.identical</strong> example in Rambda REPL</a>

identity

identity<T>(input: T): T

It just passes back the supplied input argument.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.identity(7)%20%2F%2F%20%3D%3E%207">Try this <strong>R.identity</strong> example in Rambda REPL</a>

identity<T>(input: T): T;

export function identity(x){
  return x
}

import { identity } from './identity.js'

test('happy', () => {
  expect(identity(7)).toBe(7)
  expect(identity(true)).toBeTrue()
  expect(identity({ a : 1 })).toEqual({ a : 1 })
})

import {identity} from 'rambda'

describe('R.identity', () => {
  it('happy', () => {
    const result = identity(4)
    result // $ExpectType 4
  })
})

ifElse

ifElse<T, TFiltered extends T, TOnTrueResult, TOnFalseResult>(
  pred: (a: T) => a is TFiltered,
  onTrue: (a: TFiltered) => TOnTrueResult,
  onFalse: (a: Exclude<T, TFiltered>) => TOnFalseResult,
): (a: T) => TOnTrueResult | TOnFalseResult

It expects condition, onTrue and onFalse functions as inputs and it returns a new function with example name of fn.

When fn`` is called with inputargument, it will return eitheronTrue(input)oronFalse(input)depending oncondition(input)` evaluation.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20R.ifElse(%0A%20x%20%3D%3E%20x%3E10%2C%0A%20x%20%3D%3E%20x*2%2C%0A%20x%20%3D%3E%20x*10%0A)%0A%0Aconst%20result%20%3D%20%5B%20fn(8)%2C%20fn(18)%20%5D%0A%2F%2F%20%3D%3E%20%5B80%2C%2036%5D">Try this <strong>R.ifElse</strong> example in Rambda REPL</a>

ifElse<T, TFiltered extends T, TOnTrueResult, TOnFalseResult>(
  pred: (a: T) => a is TFiltered,
  onTrue: (a: TFiltered) => TOnTrueResult,
  onFalse: (a: Exclude<T, TFiltered>) => TOnFalseResult,
): (a: T) => TOnTrueResult | TOnFalseResult;
ifElse<TArgs extends any[], TOnTrueResult, TOnFalseResult>(fn: (...args: TArgs) => boolean, onTrue: (...args: TArgs) => TOnTrueResult, onFalse: (...args: TArgs) => TOnFalseResult): (...args: TArgs) => TOnTrueResult | TOnFalseResult;

import { curry } from './curry.js'

function ifElseFn(
  condition, onTrue, onFalse
){
  return (...input) => {
		const conditionResult =
      typeof condition === 'boolean' ? condition : condition(...input)
    if (Boolean(conditionResult) ){
      return onTrue(...input)
    }

    return onFalse(...input)
  }
}

export const ifElse = curry(ifElseFn)

import { always } from './always.js'
import { has } from './has.js'
import { identity } from './identity.js'
import { ifElse } from './ifElse.js'
import { prop } from './prop.js'
import * as R from 'ramda'

const condition = has('foo')
const v = function (a){
  return typeof a === 'number'
}
const t = function (a){
  return a + 1
}
const ifFn = x => prop('foo', x).length
const elseFn = () => false

test('happy', () => {
  const fn = ifElse(condition, ifFn)(elseFn)

  expect(fn({ foo : 'bar' })).toBe(3)
  expect(fn({ fo : 'bar' })).toBeFalse()
})

test('ramda spec', () => {
  const ifIsNumber = ifElse(v)
  expect(ifIsNumber(t, identity)(15)).toBe(16)
  expect(ifIsNumber(t, identity)('hello')).toBe('hello')
})

test('pass all arguments', () => {
  const identity = function (a){
    return a
  }
  const v = function (){
    return true
  }
  const onTrue = function (a, b){
    expect(a).toBe(123)
    expect(b).toBe('abc')
  }
  ifElse(
    v, onTrue, identity
  )(123, 'abc')
})

test('accept constant as condition', () => {
  const fn = ifElse(true)(always(true))(always(false))

  expect(fn()).toBeTrue()
})

test('accept constant as condition - case 2', () => {
  const fn = ifElse(
    false, always(true), always(false)
  )

  expect(fn()).toBeFalse()
})

test('curry 1', () => {
  const fn = ifElse(condition, ifFn)(elseFn)

  expect(fn({ foo : 'bar' })).toBe(3)
  expect(fn({ fo : 'bar' })).toBeFalse()
})

test('curry 2', () => {
  const fn = ifElse(condition)(ifFn)(elseFn)

  expect(fn({ foo : 'bar' })).toBe(3)
  expect(fn({ fo : 'bar' })).toBeFalse()
})

test('simple arity of 1', () => {
  const condition = x => x > 5
  const onTrue = x => x + 1
  const onFalse = x => x + 10
  const result = ifElse(
    condition, onTrue, onFalse
  )(1)
  expect(result).toBe(11)
})

test('simple arity of 2', () => {
  const condition = (x, y) => x + y > 5
  const onTrue = (x, y) => x + y + 1
  const onFalse = (x, y) => x + y + 10
  const result = ifElse(
    condition, onTrue, onFalse
  )(1, 10)
  expect(result).toBe(12)
})

test('bug 750', () => {
	const value = 34;

	let result = ifElse(
	R.identity,
	R.always('true'),
	R.always('false')
	)(value)
	expect(result).toBe('true')
})

import {ifElse} from 'rambda'

describe('R.ifElse', () => {
  it('happy', () => {
    const condition = (x: number) => x > 5
    const onTrue = (x: number) => `foo${x}`
    const onFalse = (x: number) => `bar${x}`
    const fn = ifElse(condition, onTrue, onFalse)
    fn // $ExpectType (x: number) => string
    const result = fn(3)
    result // $ExpectType string
  })
  it('arity of 2', () => {
    const condition = (x: number, y: string) => x + y.length > 5
    const onTrue = (x: number, y: string) => `foo${x}-${y}`
    const onFalse = (x: number, y: string) => `bar${x}-${y}`
    const fn = ifElse(condition, onTrue, onFalse)
    fn // $ExpectType (x: number, y: string) => string
    const result = fn(3, 'hello')
    result // $ExpectType string
  })
  test('DefinitelyTyped#59291', () => {
    const getLengthIfStringElseDouble = ifElse(
      (a: string | number): a is string => true,
      a => a.length,
      a => a * 2
    )

    getLengthIfStringElseDouble('foo') // $ExpectType number
    getLengthIfStringElseDouble(3) // $ExpectType number
    const result = ifElse(
      (a: {
        foo?: string,
        bar: number | string,
      }): a is {foo: string, bar: string} => true,
      (a): [string, string] => [a.foo, a.bar],
      (a): [string | undefined, string | number] => [a.foo, a.bar]
    )
    result // $ExpectType (a: { foo?: string | undefined; bar: string | number; }) => [string, string] | [string | undefined, string | number]
  })
})

inc

It increments a number.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.inc(1)%20%2F%2F%20%3D%3E%202">Try this <strong>R.inc</strong> example in Rambda REPL</a>

includes

includes<T extends string>(valueToFind: T, input: string): boolean

If input is string, then this method work as native String.includes.

If input is array, then R.equals is used to define if valueToFind belongs to the list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.includes('oo'%2C%20'foo')%2C%0A%20%20R.includes(%7Ba%3A%201%7D%2C%20%5B%7Ba%3A%201%7D%5D)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%20%5D">Try this <strong>R.includes</strong> example in Rambda REPL</a>

includes<T extends string>(valueToFind: T, input: string): boolean;
includes<T extends string>(valueToFind: T): (input: string) => boolean;
includes<T>(valueToFind: T, input: T[]): boolean;
includes<T>(valueToFind: T): (input: T[]) => boolean;

import { isArray } from './_internals/isArray.js'
import { _indexOf } from './equals.js'

export function includes(valueToFind, iterable){
  if (arguments.length === 1)
    return _iterable => includes(valueToFind, _iterable)
  if (typeof iterable === 'string'){
    return iterable.includes(valueToFind)
  }
  if (!iterable){
    throw new TypeError(`Cannot read property \'indexOf\' of ${ iterable }`)
  }
  if (!isArray(iterable)) return false

  return _indexOf(valueToFind, iterable) > -1
}

import { includes as includesRamda } from 'ramda'

import { includes } from './includes.js'

test('with string as iterable', () => {
  const str = 'foo bar'

  expect(includes('bar')(str)).toBeTrue()
  expect(includesRamda('bar')(str)).toBeTrue()
  expect(includes('never', str)).toBeFalse()
  expect(includesRamda('never', str)).toBeFalse()
})

test('with array as iterable', () => {
  const arr = [ 1, 2, 3 ]

  expect(includes(2)(arr)).toBeTrue()
  expect(includesRamda(2)(arr)).toBeTrue()

  expect(includes(4, arr)).toBeFalse()
  expect(includesRamda(4, arr)).toBeFalse()
})

test('with list of objects as iterable', () => {
  const arr = [ { a : 1 }, { b : 2 }, { c : 3 } ]

  expect(includes({ c : 3 }, arr)).toBeTrue()
  expect(includesRamda({ c : 3 }, arr)).toBeTrue()
})

test('with NaN', () => {
  const result = includes(NaN, [ NaN ])
  const ramdaResult = includesRamda(NaN, [ NaN ])
  expect(result).toBeTrue()
  expect(ramdaResult).toBeTrue()
})

test('with wrong input that does not throw', () => {
  const result = includes(1, /foo/g)
  const ramdaResult = includesRamda(1, /foo/g)
  expect(result).toBeFalse()
  expect(ramdaResult).toBeFalse()
})

test('throws on wrong input - match ramda behaviour', () => {
  expect(() => includes(2, null)).toThrowWithMessage(TypeError,
    'Cannot read property \'indexOf\' of null')
  expect(() => includesRamda(2, null)).toThrowWithMessage(TypeError,
    'Cannot read properties of null (reading \'indexOf\')')
  expect(() => includes(2, undefined)).toThrowWithMessage(TypeError,
    'Cannot read property \'indexOf\' of undefined')
  expect(() => includesRamda(2, undefined)).toThrowWithMessage(TypeError,
    'Cannot read properties of undefined (reading \'indexOf\')')
})

import {includes} from 'rambda'

const list = [{a: {b: '1'}}, {a: {c: '2'}}, {a: {b: '3'}}]

describe('R.includes', () => {
  it('happy', () => {
    const result = includes({a: {b: '1'}}, list)
    result // $ExpectType boolean
    const result2 = includes('oo', ['f', 'oo'])
    result2 // $ExpectType boolean
  })
  it('with string', () => {
    const str = 'foo' as 'foo' | 'bar'
    const result = includes('oo', str)
    const curriedResult = includes('oo')(str)

    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
})

indexBy

It generates object with properties provided by condition and values provided by list array.

If condition is a function, then all list members are passed through it.

If condition is a string, then all list members are passed through R.path(condition).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%20%7Bid%3A%2010%7D%2C%20%7Bid%3A%2020%7D%20%5D%0A%0Aconst%20withFunction%20%3D%20R.indexBy(%0A%20%20x%20%3D%3E%20x.id%2C%0A%20%20list%0A)%0Aconst%20withString%20%3D%20R.indexBy(%0A%20%20'id'%2C%0A%20%20list%0A)%0Aconst%20result%20%3D%20%5B%0A%20%20withFunction%2C%20%0A%20%20R.equals(withFunction%2C%20withString)%0A%5D%0A%2F%2F%20%3D%3E%20%5B%20%7B%2010%3A%20%7Bid%3A%2010%7D%2C%2020%3A%20%7Bid%3A%2020%7D%20%7D%2C%20true%20%5D">Try this <strong>R.indexBy</strong> example in Rambda REPL</a>

indexOf

It returns the index of the first element of list equals to valueToFind.

If there is no such element, it returns -1.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B0%2C%201%2C%202%2C%203%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.indexOf(2%2C%20list)%2C%0A%20%20R.indexOf(0%2C%20list)%0A%5D%0A%2F%2F%20%3D%3E%20%5B2%2C%20-1%5D">Try this <strong>R.indexOf</strong> example in Rambda REPL</a>

init

init<T extends unknown[]>(input: T): T extends readonly [...infer U, any] ? U : [...T]

It returns all but the last element of list or string input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.init(%5B1%2C%202%2C%203%5D)%20%2C%20%0A%20%20R.init('foo')%20%20%2F%2F%20%3D%3E%20'fo'%0A%5D%0A%2F%2F%20%3D%3E%20%5B%5B1%2C%202%5D%2C%20'fo'%5D">Try this <strong>R.init</strong> example in Rambda REPL</a>

init<T extends unknown[]>(input: T): T extends readonly [...infer U, any] ? U : [...T];
init(input: string): string;

import baseSlice from './_internals/baseSlice.js'

export function init(listOrString){
  if (typeof listOrString === 'string') return listOrString.slice(0, -1)

  return listOrString.length ?
    baseSlice(
      listOrString, 0, -1
    ) :
    []
}

import { init } from './init.js'

test('with array', () => {
  expect(init([ 1, 2, 3 ])).toEqual([ 1, 2 ])
  expect(init([ 1, 2 ])).toEqual([ 1 ])
  expect(init([ 1 ])).toEqual([])
  expect(init([])).toEqual([])
  expect(init([])).toEqual([])
  expect(init([ 1 ])).toEqual([])
})

test('with string', () => {
  expect(init('foo')).toBe('fo')
  expect(init('f')).toBe('')
  expect(init('')).toBe('')
})

import {init} from 'rambda'

describe('R.init', () => {
  it('with string', () => {
    const result = init('foo')

    result // $ExpectType string
  })
  it('with list - one type', () => {
    const result = init([1, 2, 3])

    result // $ExpectType number[]
  })
  it('with list - mixed types', () => {
    const result = init([1, 2, 3, 'foo', 'bar'])

    result // $ExpectType (string | number)[]
  })
})

innerJoin

It returns a new list by applying a predicate function to all elements of list1 and list2 and keeping only these elements where predicate returns true.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list1%20%3D%20%5B1%2C%202%2C%203%2C%204%2C%205%5D%0Aconst%20list2%20%3D%20%5B4%2C%205%2C%206%5D%0Aconst%20predicate%20%3D%20(x%2C%20y)%20%3D%3E%20x%20%3E%3D%20y%0Aconst%20result%20%3D%20R.innerJoin(predicate%2C%20list1%2C%20list2)%0A%2F%2F%20%3D%3E%20%5B4%2C%205%5D">Try this <strong>R.innerJoin</strong> example in Rambda REPL</a>

insert

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B'a'%2C%20'b'%2C%20'c'%2C%20'd'%2C%20'e'%5D%3B%0Aconst%20result%20%3D%20R.insert(2%2C%20'x'%2C%20list)%3B%0A%2F%2F%20%3D%3E%20%5B'a'%2C%20'b'%2C%20'x'%2C%20'c'%2C%20'd'%2C%20'e'%5D">Try this <strong>R.insert</strong> example in Rambda REPL</a>

insertAll

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B'a'%2C%20'b'%2C%20'c'%2C%20'd'%2C%20'e'%5D%3B%0Aconst%20result%20%3D%20R.insertAll(2%2C%20%5B'x'%2C%20'y'%2C%20'z'%5D%2C%20list)%3B%0A%2F%2F%20%3D%3E%20%5B'a'%2C%20'b'%2C%20'x'%2C%20'y'%2C%20'z'%2C%20'c'%2C%20'd'%2C%20'e'%5D">Try this <strong>R.insertAll</strong> example in Rambda REPL</a>

intersection

It loops through listA and listB and returns the intersection of the two according to R.equals.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20listA%20%3D%20%5B%20%7B%20id%20%3A%201%20%7D%2C%20%7B%20id%20%3A%202%20%7D%2C%20%7B%20id%20%3A%203%20%7D%2C%20%7B%20id%20%3A%204%20%7D%20%5D%0Aconst%20listB%20%3D%20%5B%20%7B%20id%20%3A%203%20%7D%2C%20%7B%20id%20%3A%204%20%7D%2C%20%7B%20id%20%3A%205%20%7D%2C%20%7B%20id%20%3A%206%20%7D%20%5D%0A%0Aconst%20result%20%3D%20R.intersection(listA%2C%20listB)%0A%2F%2F%20%3D%3E%20%5B%7B%20id%20%3A%203%20%7D%2C%20%7B%20id%20%3A%204%20%7D%5D">Try this <strong>R.intersection</strong> example in Rambda REPL</a>

intersperse

It adds a separator between members of list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%200%2C%201%2C%202%2C%203%20%5D%0Aconst%20separator%20%3D%20'%7C'%0Aconst%20result%20%3D%20intersperse(separator%2C%20list)%0A%2F%2F%20%3D%3E%20%5B0%2C%20'%7C'%2C%201%2C%20'%7C'%2C%202%2C%20'%7C'%2C%203%5D">Try this <strong>R.intersperse</strong> example in Rambda REPL</a>

is

It returns true if x is instance of targetPrototype.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.is(String%2C%20'foo')%2C%20%20%0A%20%20R.is(Array%2C%201)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.is</strong> example in Rambda REPL</a>

isEmpty

isEmpty<T>(x: T): boolean

It returns true if x is empty.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.isEmpty('')%2C%0A%20%20R.isEmpty(%7B%20x%20%3A%200%20%7D)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.isEmpty</strong> example in Rambda REPL</a>

isEmpty<T>(x: T): boolean;

import { type } from './type.js'

export function isEmpty(input){
  const inputType = type(input)
  if ([ 'Undefined', 'NaN', 'Number', 'Null' ].includes(inputType))
    return false
  if (!input) return true

  if (inputType === 'Object'){
    return Object.keys(input).length === 0
  }

  if (inputType === 'Array'){
    return input.length === 0
  }

  return false
}

import { isEmpty } from './isEmpty.js'

test('happy', () => {
  expect(isEmpty(undefined)).toBeFalse()
  expect(isEmpty('')).toBeTrue()
  expect(isEmpty(null)).toBeFalse()
  expect(isEmpty(' ')).toBeFalse()
  expect(isEmpty(new RegExp(''))).toBeFalse()
  expect(isEmpty([])).toBeTrue()
  expect(isEmpty([ [] ])).toBeFalse()
  expect(isEmpty({})).toBeTrue()
  expect(isEmpty({ x : 0 })).toBeFalse()
  expect(isEmpty(0)).toBeFalse()
  expect(isEmpty(NaN)).toBeFalse()
  expect(isEmpty([ '' ])).toBeFalse()
})

import {isEmpty} from 'rambda'

describe('R.isEmpty', () => {
  it('happy', () => {
    const result = isEmpty('foo')
    result // $ExpectType boolean
  })
})

isNil

isNil(x: any): x is null | undefined

It returns true if x is either null or undefined.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.isNil(null)%2C%0A%20%20R.isNil(1)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.isNil</strong> example in Rambda REPL</a>

isNil(x: any): x is null | undefined;

export function isNil(x){
  return x === undefined || x === null
}

import { isNil } from './isNil.js'

test('happy', () => {
  expect(isNil(null)).toBeTrue()

  expect(isNil(undefined)).toBeTrue()

  expect(isNil([])).toBeFalse()
})

isNotEmpty

isNotEmpty<T>(value: T[]): value is NonEmptyArray<T>

isNotEmpty<T>(value: T[]): value is NonEmptyArray<T>;
isNotEmpty<T>(value: readonly T[]): value is ReadonlyNonEmptyArray<T>;
isNotEmpty(value: any): boolean;

isNotNil

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.isNotNil(null)%2C%0A%20%20R.isNotNil(undefined)%2C%0A%20%20R.isNotNil(%5B%5D)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5Bfalse%2C%20false%2C%20true%5D">Try this <strong>R.isNotNil</strong> example in Rambda REPL</a>

join

join<T>(glue: string, list: T[]): string

It returns a string of all list instances joined with a glue.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.join('-'%2C%20%5B1%2C%202%2C%203%5D)%20%20%2F%2F%20%3D%3E%20'1-2-3'">Try this <strong>R.join</strong> example in Rambda REPL</a>

join<T>(glue: string, list: T[]): string;
join<T>(glue: string): (list: T[]) => string;

export function join(glue, list){
  if (arguments.length === 1) return _list => join(glue, _list)

  return list.join(glue)
}

import { join } from './join.js'

test('curry', () => {
  expect(join('|')([ 'foo', 'bar', 'baz' ])).toBe('foo|bar|baz')

  expect(join('|', [ 1, 2, 3 ])).toBe('1|2|3')

  const spacer = join(' ')

  expect(spacer([ 'a', 2, 3.4 ])).toBe('a 2 3.4')
})

import {join} from 'rambda'

describe('R.join', () => {
  it('happy', () => {
    const result = join('|', [1, 2, 3])
    result // $ExpectType string
  })
})

juxt

juxt<A extends any[], R1>(fns: [(...a: A) => R1]): (...a: A) => [R1]

It applies list of function to a list of inputs.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20getRange%20%3D%20juxt(%5B%20Math.min%2C%20Math.max%2C%20Math.min%20%5D)%0Aconst%20result%20%3D%20getRange(%0A%20%203%2C%204%2C%209%2C%20-3%0A)%0A%2F%2F%20%3D%3E%20%5B-3%2C%209%2C%20-3%5D">Try this <strong>R.juxt</strong> example in Rambda REPL</a>

juxt<A extends any[], R1>(fns: [(...a: A) => R1]): (...a: A) => [R1];
juxt<A extends any[], R1, R2>(fns: [(...a: A) => R1, (...a: A) => R2]): (...a: A) => [R1, R2];
juxt<A extends any[], R1, R2, R3>(fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3]): (...a: A) => [R1, R2, R3];
juxt<A extends any[], R1, R2, R3, R4>(fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3, (...a: A) => R4]): (...a: A) => [R1, R2, R3, R4];
juxt<A extends any[], R1, R2, R3, R4, R5>(fns: [(...a: A) => R1, (...a: A) => R2, (...a: A) => R3, (...a: A) => R4, (...a: A) => R5]): (...a: A) => [R1, R2, R3, R4, R5];
juxt<A extends any[], U>(fns: Array<(...args: A) => U>): (...args: A) => U[];

export function juxt(listOfFunctions){
  return (...args) => listOfFunctions.map(fn => fn(...args))
}

import { juxt } from './juxt.js'

test('happy', () => {
  const fn = juxt([ Math.min, Math.max, Math.min ])
  const result = fn(
    3, 4, 9, -3
  )
  expect(result).toEqual([ -3, 9, -3 ])
})

import {juxt} from 'rambda'

describe('R.juxt', () => {
  it('happy', () => {
    const fn = juxt([Math.min, Math.max])
    const result = fn(3, 4, 9, -3)
    result // $ExpectType [number, number]
  })
})

keys

keys<T extends object>(x: T): (keyof T & string)[]

It applies Object.keys over x and returns its keys.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.keys(%7Ba%3A1%2C%20b%3A2%7D)%20%20%2F%2F%20%3D%3E%20%5B'a'%2C%20'b'%5D">Try this <strong>R.keys</strong> example in Rambda REPL</a>

keys<T extends object>(x: T): (keyof T & string)[];
keys<T>(x: T): string[];

export function keys(x){
  return Object.keys(x)
}

import { keys } from './keys.js'

test('happy', () => {
  expect(keys({ a : 1 })).toEqual([ 'a' ])
})

last

last(str: ''): undefined

It returns the last element of input, as the input can be either a string or an array. It returns undefined if array has length of 0.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.last(%5B1%2C%202%2C%203%5D)%2C%0A%20%20R.last('foo')%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5B3%2C%20'o'%5D">Try this <strong>R.last</strong> example in Rambda REPL</a>

last(str: ''): undefined;
last(str: string): string;
last(list: readonly[]): undefined;
last(list: never[]): undefined;
last<T extends unknown[]>(array: T): LastArrayElement<T>;
last<T extends readonly unknown[]>(array: T): LastArrayElement<T>;
last(str: string): string | undefined;

export function last(listOrString){
  if (typeof listOrString === 'string'){
    return listOrString[ listOrString.length - 1 ] || ''
  }

  return listOrString[ listOrString.length - 1 ]
}

import { last } from './last.js'

test('with list', () => {
  expect(last([ 1, 2, 3 ])).toBe(3)
  expect(last([])).toBeUndefined()
})

test('with string', () => {
  expect(last('abc')).toBe('c')
  expect(last('')).toBe('')
})

lastIndexOf

lastIndexOf<T>(target: T, list: T[]): number

It returns the last index of target in list array.

R.equals is used to determine equality between target and members of list.

If there is no such index, then -1 is returned.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%2C%201%2C%202%2C%203%5D%0Aconst%20result%20%3D%20%5B%0A%20%20R.lastIndexOf(2%2C%20list)%2C%0A%20%20R.lastIndexOf(4%2C%20list)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5B4%2C%20-1%5D">Try this <strong>R.lastIndexOf</strong> example in Rambda REPL</a>

lastIndexOf<T>(target: T, list: T[]): number;
lastIndexOf<T>(target: T): (list: T[]) => number;

import { _lastIndexOf } from './equals.js'

export function lastIndexOf(valueToFind, list){
  if (arguments.length === 1){
    return _list => _lastIndexOf(valueToFind, _list)
  }

  return _lastIndexOf(valueToFind, list)
}

import { lastIndexOf as lastIndexOfRamda } from 'ramda'

import { compareCombinations } from './_internals/testUtils.js'
import { possibleIterables, possibleTargets } from './indexOf.spec.js'
import { lastIndexOf } from './lastIndexOf.js'

test('with NaN', () => {
  expect(lastIndexOf(NaN, [ NaN ])).toBe(0)
})

test('will throw with bad input', () => {
  expect(lastIndexOfRamda([], true)).toBe(-1)
  expect(() => indexOf([], true)).toThrowErrorMatchingInlineSnapshot('"indexOf is not defined"')
})

test('without list of objects - no R.equals', () => {
  expect(lastIndexOf(3, [ 1, 2, 3, 4 ])).toBe(2)
  expect(lastIndexOf(10)([ 1, 2, 3, 4 ])).toBe(-1)
})

test('list of objects uses R.equals', () => {
  const listOfObjects = [ { a : 1 }, { b : 2 }, { c : 3 } ]
  expect(lastIndexOf({ c : 4 }, listOfObjects)).toBe(-1)
  expect(lastIndexOf({ c : 3 }, listOfObjects)).toBe(2)
})

test('list of arrays uses R.equals', () => {
  const listOfLists = [ [ 1 ], [ 2, 3 ], [ 2, 3, 4 ], [ 2, 3 ], [ 1 ], [] ]
  expect(lastIndexOf([], listOfLists)).toBe(5)
  expect(lastIndexOf([ 1 ], listOfLists)).toBe(4)
  expect(lastIndexOf([ 2, 3, 4 ], listOfLists)).toBe(2)
  expect(lastIndexOf([ 2, 3, 5 ], listOfLists)).toBe(-1)
})

test('with string as iterable', () => {
  expect(() => lastIndexOf('a', 'abc')).toThrowErrorMatchingInlineSnapshot('"Cannot read property \'indexOf\' of abc"')
  expect(lastIndexOfRamda('a', 'abc')).toBe(0)
})

describe('brute force', () => {
  compareCombinations({
    fn          : lastIndexOf,
    fnRamda     : lastIndexOfRamda,
    firstInput  : possibleTargets,
    secondInput : possibleIterables,
    callback    : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
        {
          "ERRORS_MESSAGE_MISMATCH": 0,
          "ERRORS_TYPE_MISMATCH": 34,
          "RESULTS_MISMATCH": 0,
          "SHOULD_NOT_THROW": 51,
          "SHOULD_THROW": 0,
          "TOTAL_TESTS": 170,
        }
      `)
    },
  })
})

import {lastIndexOf} from 'rambda'

const list = [1, 2, 3]

describe('R.lastIndexOf', () => {
  it('happy', () => {
    const result = lastIndexOf(2, list)
    result // $ExpectType number
  })
  it('curried', () => {
    const result = lastIndexOf(2)(list)
    result // $ExpectType number
  })
})

length

length<T>(input: T[]): number

It returns the length property of list or string input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.length(%5B1%2C%202%2C%203%2C%204%5D)%2C%0A%20%20R.length('foo')%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5B4%2C%203%5D">Try this <strong>R.length</strong> example in Rambda REPL</a>

length<T>(input: T[]): number;

import { isArray } from './_internals/isArray.js'

export function length(x){
  if (isArray(x)) return x.length
  if (typeof x === 'string') return x.length

  return NaN
}

import { length as lengthRamda } from 'ramda'

import { length } from './length.js'

test('happy', () => {
  expect(length('foo')).toBe(3)
  expect(length([ 1, 2, 3 ])).toBe(3)
  expect(length([])).toBe(0)
})

test('with empty string', () => {
  expect(length('')).toBe(0)
})

test('with bad input returns NaN', () => {
  expect(length(0)).toBeNaN()
  expect(length({})).toBeNaN()
  expect(length(null)).toBeNaN()
  expect(length(undefined)).toBeNaN()
})

test('with length as property', () => {
  const input1 = { length : '123' }
  const input2 = { length : null }
  const input3 = { length : '' }

  expect(length(input1)).toBeNaN()
  expect(lengthRamda(input1)).toBeNaN()
  expect(length(input2)).toBeNaN()
  expect(lengthRamda(input2)).toBeNaN()
  expect(length(input3)).toBeNaN()
  expect(lengthRamda(input3)).toBeNaN()
})

lens

lens<S, A>(getter: (s: S) => A, setter: (a: A, s: S) => S): Lens<S, A>

It returns a lens for the given getter and setter functions.

The getter gets the value of the focus; the setter sets the value of the focus.

The setter should not mutate the data structure.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20xLens%20%3D%20R.lens(R.prop('x')%2C%20R.assoc('x'))%3B%0A%0AR.view(xLens%2C%20%7Bx%3A%201%2C%20y%3A%202%7D)%20%2F%2F%20%3D%3E%201%0AR.set(xLens%2C%204%2C%20%7Bx%3A%201%2C%20y%3A%202%7D)%20%2F%2F%20%3D%3E%20%7Bx%3A%204%2C%20y%3A%202%7D%0Aconst%20result%20%3D%20R.over(xLens%2C%20R.negate%2C%20%7Bx%3A%201%2C%20y%3A%202%7D)%20%2F%2F%20%3D%3E%20%7Bx%3A%20-1%2C%20y%3A%202%7D">Try this <strong>R.lens</strong> example in Rambda REPL</a>

lens<S, A>(getter: (s: S) => A, setter: (a: A, s: S) => S): Lens<S, A>;

export function lens(getter, setter){
  return function (functor){
    return function (target){
      return functor(getter(target)).map(focus => setter(focus, target))
    }
  }
}

import {lens, assoc, lensProp, view, lensIndex, over, lensPath} from 'rambda'

interface Input {
  foo: string,
}
const testObject: Input = {
  foo: 'Jazz',
}

describe('R.lens', () => {
  it('happy', () => {
    const fn = lens<Input, string>((x: Input) => {
      x.foo // $ExpectType string
      return x.foo
    }, assoc('name'))
    fn // $ExpectType Lens<Input, string>
  })
})

describe('R.lensProp', () => {
  it('happy', () => {
    const result = view<Input, string>(lensProp('foo'), testObject)
    result // $ExpectType string
  })
  it('issue 740', () => {
    // @ts-expect-error
    over(lensProp('x'), (n) => String(n), {x: 1})
  })
})

describe('R.lensIndex', () => {
  const testList: Input[] = [{foo: 'bar'}, {foo: 'baz'}]
  it('happy', () => {
    const result = view<Input[], Input>(lensIndex(0), testList)
    result // $ExpectType Input
    result.foo // $ExpectType string
  })
})

describe('R.lensPath', () => {
  const path = lensPath(['bar', 'a'])
  it('happy', () => {
    const result = view<Input, string>(path, testObject)
    result // $ExpectType string
  })
})

describe('R.view', () => {
  const fooLens = lens<Input, string>((x: Input) => {
    return x.foo
  }, assoc('foo'))
  it('happt', () => {
    const result = view<Input, string>(fooLens, testObject)
    result // $ExpectType string
  })
})

lensIndex

lensIndex<A>(n: number): Lens<A[], A>

It returns a lens that focuses on specified index.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B'a'%2C%20'b'%2C%20'c'%5D%0Aconst%20headLens%20%3D%20R.lensIndex(0)%0A%0AR.view(headLens%2C%20list)%20%2F%2F%20%3D%3E%20'a'%0AR.set(headLens%2C%20'x'%2C%20list)%20%2F%2F%20%3D%3E%20%5B'x'%2C%20'b'%2C%20'c'%5D%0Aconst%20result%20%3D%20R.over(headLens%2C%20R.toUpper%2C%20list)%20%2F%2F%20%3D%3E%20%5B'A'%2C%20'b'%2C%20'c'%5D">Try this <strong>R.lensIndex</strong> example in Rambda REPL</a>

lensIndex<A>(n: number): Lens<A[], A>;
lensIndex<A extends any[], N extends number>(n: N): Lens<A, A[N]>;

import { lens } from './lens.js'
import { nth } from './nth.js'
import { update } from './update.js'

export function lensIndex(index){
  return lens(nth(index), update(index))
}

import { compose } from './compose.js'
import { keys } from './keys.js'
import { lensIndex } from './lensIndex.js'
import { over } from './over.js'
import { set } from './set.js'
import { view } from './view.js'

const testList = [ { a : 1 }, { b : 2 }, { c : 3 } ]

test('focuses list element at the specified index', () => {
  expect(view(lensIndex(0), testList)).toEqual({ a : 1 })
})

test('returns undefined if the specified index does not exist', () => {
  expect(view(lensIndex(10), testList)).toBeUndefined()
})

test('sets the list value at the specified index', () => {
  expect(set(
    lensIndex(0), 0, testList
  )).toEqual([ 0, { b : 2 }, { c : 3 } ])
})

test('applies function to the value at the specified list index', () => {
  expect(over(
    lensIndex(2), keys, testList
  )).toEqual([ { a : 1 }, { b : 2 }, [ 'c' ] ])
})

test('can be composed', () => {
  const nestedList = [ 0, [ 10, 11, 12 ], 1, 2 ]
  const composedLens = compose(lensIndex(1), lensIndex(0))

  expect(view(composedLens, nestedList)).toBe(10)
})

test('set s (get s) === s', () => {
  expect(set(
    lensIndex(0), view(lensIndex(0), testList), testList
  )).toEqual(testList)
})

test('get (set s v) === v', () => {
  expect(view(lensIndex(0), set(
    lensIndex(0), 0, testList
  ))).toBe(0)
})

test('get (set(set s v1) v2) === v2', () => {
  expect(view(lensIndex(0),
    set(
      lensIndex(0), 11, set(
        lensIndex(0), 10, testList
      )
    ))).toBe(11)
})

lensPath

It returns a lens that focuses on specified path.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20lensPath%20%3D%20R.lensPath(%5B'x'%2C%200%2C%20'y'%5D)%0Aconst%20input%20%3D%20%7Bx%3A%20%5B%7By%3A%202%2C%20z%3A%203%7D%2C%20%7By%3A%204%2C%20z%3A%205%7D%5D%7D%0A%0AR.view(lensPath%2C%20input)%20%2F%2F%20%3D%3E%202%0A%0AR.set(lensPath%2C%201%2C%20input)%20%0A%2F%2F%20%3D%3E%20%7Bx%3A%20%5B%7By%3A%201%2C%20z%3A%203%7D%2C%20%7By%3A%204%2C%20z%3A%205%7D%5D%7D%0A%0Aconst%20result%20%3D%20R.over(xHeadYLens%2C%20R.negate%2C%20input)%20%0A%2F%2F%20%3D%3E%20%7Bx%3A%20%5B%7By%3A%20-2%2C%20z%3A%203%7D%2C%20%7By%3A%204%2C%20z%3A%205%7D%5D%7D">Try this <strong>R.lensPath</strong> example in Rambda REPL</a>

lensProp

lensProp<S, K extends keyof S = keyof S>(prop: K): Lens<S, S[K]>

It returns a lens that focuses on specified property prop.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20xLens%20%3D%20R.lensProp('x')%3B%0Aconst%20input%20%3D%20%7Bx%3A%201%2C%20y%3A%202%7D%0A%0AR.view(xLens%2C%20input)%20%2F%2F%20%3D%3E%201%0A%0AR.set(xLens%2C%204%2C%20input)%20%0A%2F%2F%20%3D%3E%20%7Bx%3A%204%2C%20y%3A%202%7D%0A%0Aconst%20result%20%3D%20R.over(xLens%2C%20R.negate%2C%20input)%20%0A%2F%2F%20%3D%3E%20%7Bx%3A%20-1%2C%20y%3A%202%7D">Try this <strong>R.lensProp</strong> example in Rambda REPL</a>

lensProp<S, K extends keyof S = keyof S>(prop: K): Lens<S, S[K]>;

import { assoc } from './assoc.js'
import { lens } from './lens.js'
import { prop } from './prop.js'

export function lensProp(key){
  return lens(prop(key), assoc(key))
}

import { compose } from './compose.js'
import { identity } from './identity.js'
import { inc } from './inc.js'
import { lensProp } from './lensProp.js'
import { over } from './over.js'
import { set } from './set.js'
import { view } from './view.js'

const testObj = {
  a : 1,
  b : 2,
  c : 3,
}

test('focuses object the specified object property', () => {
  expect(view(lensProp('a'), testObj)).toBe(1)
})

test('returns undefined if the specified property does not exist', () => {
  expect(view(lensProp('X'), testObj)).toBeUndefined()
})

test('sets the value of the object property specified', () => {
  expect(set(
    lensProp('a'), 0, testObj
  )).toEqual({
    a : 0,
    b : 2,
    c : 3,
  })
})

test('adds the property to the object if it doesn\'t exist', () => {
  expect(set(
    lensProp('d'), 4, testObj
  )).toEqual({
    a : 1,
    b : 2,
    c : 3,
    d : 4,
  })
})

test('applies function to the value of the specified object property', () => {
  expect(over(
    lensProp('a'), inc, testObj
  )).toEqual({
    a : 2,
    b : 2,
    c : 3,
  })
})

test('applies function to undefined and adds the property if it doesn\'t exist', () => {
  expect(over(
    lensProp('X'), identity, testObj
  )).toEqual({
    a : 1,
    b : 2,
    c : 3,
    X : undefined,
  })
})

test('can be composed', () => {
  const nestedObj = {
    a : { b : 1 },
    c : 2,
  }
  const composedLens = compose(lensProp('a'), lensProp('b'))

  expect(view(composedLens, nestedObj)).toBe(1)
})

test('set s (get s) === s', () => {
  expect(set(
    lensProp('a'), view(lensProp('a'), testObj), testObj
  )).toEqual(testObj)
})

test('get (set s v) === v', () => {
  expect(view(lensProp('a'), set(
    lensProp('a'), 0, testObj
  ))).toBe(0)
})

test('get (set(set s v1) v2) === v2', () => {
  expect(view(lensProp('a'),
    set(
      lensProp('a'), 11, set(
        lensProp('a'), 10, testObj
      )
    ))).toBe(11)
})

lt

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5BR.lt(2%2C%201)%2C%20R.lt(2%2C%203)%5D%0A%2F%2F%20%3D%3E%20%5Bfalse%2C%20true%5D">Try this <strong>R.lt</strong> example in Rambda REPL</a>

lte

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5BR.lte(2%2C%201)%2C%20R.lte(2%2C%202)%2C%20R.lte(2%2C%203)%5D%0A%2F%2F%20%3D%3E%20%5Bfalse%2C%20true%2C%20true%5D">Try this <strong>R.lte</strong> example in Rambda REPL</a>

map

map<T, U>(fn: ObjectIterator<T, U>, iterable: Dictionary<T>): Dictionary<U>

It returns the result of looping through iterable with fn.

It works with both array and object.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20x%20%3D%3E%20x%20*%202%0Aconst%20fnWhenObject%20%3D%20(val%2C%20prop)%3D%3E%7B%0A%20%20return%20%60%24%7Bprop%7D-%24%7Bval%7D%60%0A%7D%0A%0Aconst%20iterable%20%3D%20%5B1%2C%202%5D%0Aconst%20obj%20%3D%20%7Ba%3A%201%2C%20b%3A%202%7D%0A%0Aconst%20result%20%3D%20%5B%20%0A%20%20R.map(fn%2C%20iterable)%2C%0A%20%20R.map(fnWhenObject%2C%20obj)%0A%5D%0A%2F%2F%20%3D%3E%20%5B%20%5B2%2C%204%5D%2C%20%7Ba%3A%20'a-1'%2C%20b%3A%20'b-2'%7D%5D">Try this <strong>R.map</strong> example in Rambda REPL</a>

map<T, U>(fn: ObjectIterator<T, U>, iterable: Dictionary<T>): Dictionary<U>;
map<T, U>(fn: Iterator<T, U>, iterable: T[]): U[];
map<T, U>(fn: Iterator<T, U>): (iterable: T[]) => U[];
map<T, U, S>(fn: ObjectIterator<T, U>): (iterable: Dictionary<T>) => Dictionary<U>;
map<T>(fn: Iterator<T, T>): (iterable: T[]) => T[];
map<T>(fn: Iterator<T, T>, iterable: T[]): T[];

import { INCORRECT_ITERABLE_INPUT } from './_internals/constants.js'
import { isArray } from './_internals/isArray.js'
import { keys } from './_internals/keys.js'

export function mapArray(
  fn, list, isIndexed = false
){
  let index = 0
  const willReturn = Array(list.length)

  while (index < list.length){
    willReturn[ index ] = isIndexed ? fn(list[ index ], index) : fn(list[ index ])

    index++
  }

  return willReturn
}

export function mapObject(fn, obj){
  if (arguments.length === 1){
    return _obj => mapObject(fn, _obj)
  }
  let index = 0
  const objKeys = keys(obj)
  const len = objKeys.length
  const willReturn = {}

  while (index < len){
    const key = objKeys[ index ]
    willReturn[ key ] = fn(
      obj[ key ], key, obj
    )
    index++
  }

  return willReturn
}

export const mapObjIndexed = mapObject

export function map(fn, iterable){
  if (arguments.length === 1) return _iterable => map(fn, _iterable)
  if (!iterable){
    throw new Error(INCORRECT_ITERABLE_INPUT)
  }

  if (isArray(iterable)) return mapArray(fn, iterable)

  return mapObject(fn, iterable)
}

import { map as mapRamda } from 'ramda'

import { map } from './map.js'

const double = x => x * 2

describe('with array', () => {
  it('happy', () => {
    expect(map(double, [ 1, 2, 3 ])).toEqual([ 2, 4, 6 ])
  })

  it('curried', () => {
    expect(map(double)([ 1, 2, 3 ])).toEqual([ 2, 4, 6 ])
  })
})

describe('with object', () => {
  const obj = {
    a : 1,
    b : 2,
  }

  it('happy', () => {
    expect(map(double, obj)).toEqual({
      a : 2,
      b : 4,
    })
  })

  it('property as second and input object as third argument', () => {
    const obj = {
      a : 1,
      b : 2,
    }
    const iterator = (
      val, prop, inputObject
    ) => {
      expect(prop).toBeString()
      expect(inputObject).toEqual(obj)

      return val * 2
    }

    expect(map(iterator)(obj)).toEqual({
      a : 2,
      b : 4,
    })
  })
})

test('bad inputs difference between Ramda and Rambda', () => {
  expect(() => map(double, null)).toThrowErrorMatchingInlineSnapshot('"Incorrect iterable input"')
  expect(() => map(double)(undefined)).toThrowErrorMatchingInlineSnapshot('"Incorrect iterable input"')
  expect(() => mapRamda(double, null)).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of null (reading \'fantasy-land/map\')"')
  expect(() =>
    mapRamda(double, undefined)).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of undefined (reading \'fantasy-land/map\')"')
})

import {map} from 'rambda'

describe('R.map with arrays', () => {
  it('iterable returns the same type as the input', () => {
    const result = map<number>(
      (x: number) => {
        x // $ExpectType number
        return x + 2
      },
      [1, 2, 3]
    )
    result // $ExpectType number[]
  })
  it('iterable returns the same type as the input - curried', () => {
    const result = map<number>((x: number) => {
      x // $ExpectType number
      return x + 2
    })([1, 2, 3])
    result // $ExpectType number[]
  })
  it('iterable returns different type as the input', () => {
    const result = map<number, string>(
      (x: number) => {
        x // $ExpectType number
        return String(x)
      },
      [1, 2, 3]
    )
    result // $ExpectType string[]
  })
})

describe('R.map with objects', () => {
  it('iterable with all three arguments - curried', () => {
    // It requires dummy third typing argument
    // in order to identify compared to curry typings for arrays
    // ============================================
    const result = map<number, string, any>((a, b, c) => {
      a // $ExpectType number
      b // $ExpectType string
      c // $ExpectType Dictionary<number>
      return `${a}`
    })({a: 1, b: 2})
    result // $ExpectType Dictionary<string>
  })
  it('iterable with all three arguments', () => {
    const result = map<number, string>(
      (a, b, c) => {
        a // $ExpectType number
        b // $ExpectType string
        c // $ExpectType Dictionary<number>
        return `${a}`
      },
      {a: 1, b: 2}
    )
    result // $ExpectType Dictionary<string>
  })
  it('iterable with property argument', () => {
    const result = map<number, string>(
      (a, b) => {
        a // $ExpectType number
        b // $ExpectType string
        return `${a}`
      },
      {a: 1, b: 2}
    )
    result // $ExpectType Dictionary<string>
  })
  it('iterable with no property argument', () => {
    const result = map<number, string>(
      a => {
        a // $ExpectType number
        return `${a}`
      },
      {a: 1, b: 2}
    )
    result // $ExpectType Dictionary<string>
  })
})

mapObjIndexed

mapObjIndexed<T>(fn: ObjectIterator<T, T>, iterable: Dictionary<T>): Dictionary<T>

It works the same way as R.map does for objects. It is added as Ramda also has this method.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20(val%2C%20prop)%20%3D%3E%20%7B%0A%20%20return%20%60%24%7Bprop%7D-%24%7Bval%7D%60%0A%7D%0A%0Aconst%20obj%20%3D%20%7Ba%3A%201%2C%20b%3A%202%7D%0A%0Aconst%20result%20%3D%20R.mapObjIndexed(fn%2C%20obj)%0A%2F%2F%20%3D%3E%20%7Ba%3A%20'a-1'%2C%20b%3A%20'b-2'%7D">Try this <strong>R.mapObjIndexed</strong> example in Rambda REPL</a>

mapObjIndexed<T>(fn: ObjectIterator<T, T>, iterable: Dictionary<T>): Dictionary<T>;
mapObjIndexed<T, U>(fn: ObjectIterator<T, U>, iterable: Dictionary<T>): Dictionary<U>;
mapObjIndexed<T>(fn: ObjectIterator<T, T>): (iterable: Dictionary<T>) => Dictionary<T>;
mapObjIndexed<T, U>(fn: ObjectIterator<T, U>): (iterable: Dictionary<T>) => Dictionary<U>;

import {mapObjIndexed} from 'rambda'

const obj = {a: 1, b: 2, c: 3}

describe('R.mapObjIndexed', () => {
  it('without type transform', () => {
    const result = mapObjIndexed((x, prop, obj) => {
      x // $ExpectType number
      prop // $ExpectType string
      obj // $ExpectType Dictionary<number>
      return x + 2
    }, obj)
    result // $ExpectType Dictionary<number>
  })
  it('without type transform - curried', () => {
    const result = mapObjIndexed<number>((x, prop, obj) => {
      x // $ExpectType number
      prop // $ExpectType string
      obj // $ExpectType Dictionary<number>
      return x + 2
    })(obj)
    result // $ExpectType Dictionary<number>
  })
  it('change of type', () => {
    const result = mapObjIndexed((x, prop, obj) => {
      x // $ExpectType number
      prop // $ExpectType string
      obj // $ExpectType Dictionary<number>
      return String(x + 2)
    }, obj)
    result // $ExpectType Dictionary<string>
  })
  it('change of type - curried', () => {
    const result = mapObjIndexed<number, string>((x, prop, obj) => {
      x // $ExpectType number
      prop // $ExpectType string
      obj // $ExpectType Dictionary<number>
      return String(x + 2)
    })(obj)
    result // $ExpectType Dictionary<string>
  })
})

match

match(regExpression: RegExp, str: string): string[]

Curried version of String.prototype.match which returns empty array, when there is no match.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.match('a'%2C%20'foo')%2C%0A%20%20R.match(%2F(%5Ba-z%5Da)%2Fg%2C%20'bananas')%0A%5D%0A%2F%2F%20%3D%3E%20%5B%5B%5D%2C%20%5B'ba'%2C%20'na'%2C%20'na'%5D%5D">Try this <strong>R.match</strong> example in Rambda REPL</a>

match(regExpression: RegExp, str: string): string[];
match(regExpression: RegExp): (str: string) => string[];

export function match(pattern, input){
  if (arguments.length === 1) return _input => match(pattern, _input)

  const willReturn = input.match(pattern)

  return willReturn === null ? [] : willReturn
}

import { equals } from './equals.js'
import { match } from './match.js'

test('happy', () => {
  expect(match(/a./g)('foo bar baz')).toEqual([ 'ar', 'az' ])
})

test('fallback', () => {
  expect(match(/a./g)('foo')).toEqual([])
})

test('with string', () => {
  expect(match('a', 'foo')).toEqual([])
  expect(equals(match('o', 'foo'), [ 'o' ])).toBeTrue()
})

test('throwing', () => {
  expect(() => {
    match(/a./g, null)
  }).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of null (reading \'match\')"')
})

import {match} from 'rambda'

const str = 'foo bar'

describe('R.match', () => {
  it('happy', () => {
    const result = match(/foo/, str)
    result // $ExpectType string[]
  })
  it('curried', () => {
    const result = match(/foo/)(str)
    result // $ExpectType string[]
  })
})

mathMod

R.mathMod behaves like the modulo operator should mathematically, unlike the % operator (and by extension, R.modulo). So while -17 % 5 is -2, mathMod(-17, 5) is 3.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.mathMod(-17%2C%205)%2C%0A%20%20R.mathMod(17%2C%205)%2C%0A%20%20R.mathMod(17%2C%20-5)%2C%20%20%0A%20%20R.mathMod(17%2C%200)%20%20%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B3%2C%202%2C%20NaN%2C%20NaN%5D">Try this <strong>R.mathMod</strong> example in Rambda REPL</a>

max

It returns the greater value between x and y.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.max(5%2C%207)%2C%20%20%0A%20%20R.max('bar'%2C%20'foo')%2C%20%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B7%2C%20'foo'%5D">Try this <strong>R.max</strong> example in Rambda REPL</a>

maxBy

It returns the greater value between x and y according to compareFn function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20compareFn%20%3D%20Math.abs%0A%0Aconst%20result%20%3D%20R.maxBy(compareFn%2C%205%2C%20-7)%20%2F%2F%20%3D%3E%20-7">Try this <strong>R.maxBy</strong> example in Rambda REPL</a>

mean

mean(list: number[]): number

It returns the mean value of list input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.mean(%5B%202%2C%207%20%5D)%0A%2F%2F%20%3D%3E%204.5">Try this <strong>R.mean</strong> example in Rambda REPL</a>

mean(list: number[]): number;

import { sum } from './sum.js'

export function mean(list){
  return sum(list) / list.length
}

import { mean } from './mean.js'

test('happy', () => {
  expect(mean([ 2, 7 ])).toBe(4.5)
})

test('with NaN', () => {
  expect(mean([])).toBeNaN()
})

import {mean} from 'rambda'

describe('R.mean', () => {
  it('happy', () => {
    const result = mean([1, 2, 3])

    result // $ExpectType number
  })
})

median

median(list: number[]): number

It returns the median value of list input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.median(%5B%207%2C%202%2C%2010%2C%209%20%5D)%20%2F%2F%20%3D%3E%208">Try this <strong>R.median</strong> example in Rambda REPL</a>

median(list: number[]): number;

import { mean } from './mean.js'

export function median(list){
  const len = list.length
  if (len === 0) return NaN
  const width = 2 - len % 2
  const idx = (len - width) / 2

  return mean(Array.prototype.slice
    .call(list, 0)
    .sort((a, b) => {
      if (a === b) return 0

      return a < b ? -1 : 1
    })
    .slice(idx, idx + width))
}

import { median } from './median.js'

test('happy', () => {
  expect(median([ 2 ])).toBe(2)
  expect(median([ 7, 2, 10, 2, 9 ])).toBe(7)
})

test('with empty array', () => {
  expect(median([])).toBeNaN()
})

import {median} from 'rambda'

describe('R.median', () => {
  it('happy', () => {
    const result = median([1, 2, 3])

    result // $ExpectType number
  })
})

merge

Same as R.mergeRight.

mergeAll

mergeAll<T>(list: object[]): T

It merges all objects of list array sequentially and returns the result.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%0A%20%20%7Ba%3A%201%7D%2C%0A%20%20%7Bb%3A%202%7D%2C%0A%20%20%7Bc%3A%203%7D%0A%5D%0Aconst%20result%20%3D%20R.mergeAll(list)%0Aconst%20expected%20%3D%20%7B%0A%20%20a%3A%201%2C%0A%20%20b%3A%202%2C%0A%20%20c%3A%203%0A%7D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.mergeAll</strong> example in Rambda REPL</a>

mergeAll<T>(list: object[]): T;
mergeAll(list: object[]): object;

import { map } from './map.js'
import { mergeRight } from './mergeRight.js'

export function mergeAll(arr){
  let willReturn = {}
  map(val => {
    willReturn = mergeRight(willReturn, val)
  }, arr)

  return willReturn
}

import { mergeAll } from './mergeAll.js'

test('case 1', () => {
  const arr = [ { a : 1 }, { b : 2 }, { c : 3 } ]
  const expectedResult = {
    a : 1,
    b : 2,
    c : 3,
  }
  expect(mergeAll(arr)).toEqual(expectedResult)
})

test('case 2', () => {
  expect(mergeAll([ { foo : 1 }, { bar : 2 }, { baz : 3 } ])).toEqual({
    foo : 1,
    bar : 2,
    baz : 3,
  })
})

describe('acts as if nil values are simply empty objects', () => {
  it('if the first object is nil', () => {
    expect(mergeAll([ null, { foo : 1 }, { foo : 2 }, { bar : 2 } ])).toEqual({
      foo : 2,
      bar : 2,
    })
  })

  it('if the last object is nil', () => {
    expect(mergeAll([ { foo : 1 }, { foo : 2 }, { bar : 2 }, undefined ])).toEqual({
      foo : 2,
      bar : 2,
    })
  })

  it('if an intermediate object is nil', () => {
    expect(mergeAll([ { foo : 1 }, { foo : 2 }, null, { bar : 2 } ])).toEqual({
      foo : 2,
      bar : 2,
    })
  })
})

import {mergeAll} from 'rambda'

describe('R.mergeAll', () => {
  it('with passing type', () => {
    interface Output {
      foo: number,
      bar: number,
    }
    const result = mergeAll<Output>([{foo: 1}, {bar: 2}])
    result.foo // $ExpectType number
    result.bar // $ExpectType number
  })

  it('without passing type', () => {
    const result = mergeAll([{foo: 1}, {bar: 2}])
    result // $ExpectType unknown
  })
})

mergeDeepLeft

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.mergeDeepLeft(%0A%20%20%7Ba%3A%20%7Bb%3A%201%7D%7D%2C%0A%20%20%7Ba%3A%20%7Bb%3A%202%2C%20c%3A%203%7D%7D%0A)%0A%2F%2F%20%3D%3E%20%7Ba%3A%20%7Bb%3A%201%2C%20c%3A%203%7D%7D">Try this <strong>R.mergeDeepLeft</strong> example in Rambda REPL</a>

mergeDeepRight

mergeDeepRight<Output>(target: object, newProps: object): Output

Creates a new object with the own properties of the first object merged with the own properties of the second object. If a key exists in both objects:

• and both values are objects, the two values will be recursively merged
• otherwise the value from the second object will be used.

mergeDeepRight<Output>(target: object, newProps: object): Output;
mergeDeepRight<Output>(target: object): (newProps: object) => Output;

import { clone } from './clone.js'
import { type } from './type.js'

export function mergeDeepRight(target, source){
  if (arguments.length === 1){
    return sourceHolder => mergeDeepRight(target, sourceHolder)
  }

  const willReturn = clone(target)

  Object.keys(source).forEach(key => {
    if (type(source[ key ]) === 'Object'){
      if (type(target[ key ]) === 'Object'){
        willReturn[ key ] = mergeDeepRight(target[ key ], source[ key ])
      } else {
        willReturn[ key ] = source[ key ]
      }
    } else {
      willReturn[ key ] = source[ key ]
    }
  })

  return willReturn
}

import { mergeDeepRight } from './mergeDeepRight.js'

const student = {
  name    : 'foo',
  age     : 10,
  contact : {
    a     : 1,
    email : 'foo@example.com',
  },
}
const teacher = {
  age     : 40,
  contact : { email : 'baz@example.com' },
  songs   : { title : 'Remains the same' },
}

test('when merging object with lists inside them', () => {
  const a = {
    a : [ 1, 2, 3 ],
    b : [ 4, 5, 6 ],
  }
  const b = {
    a : [ 7, 8, 9 ],
    b : [ 10, 11, 12 ],
  }
  const result = mergeDeepRight(a, b)
  const expected = {
    a : [ 7, 8, 9 ],
    b : [ 10, 11, 12 ],
  }
  expect(result).toEqual(expected)
})

test('happy', () => {
  const result = mergeDeepRight(student, teacher)
  const curryResult = mergeDeepRight(student)(teacher)
  const expected = {
    age     : 40,
    name    : 'foo',
    contact : {
      a     : 1,
      email : 'baz@example.com',
    },
    songs : { title : 'Remains the same' },
  }

  expect(result).toEqual(expected)
  expect(curryResult).toEqual(expected)
})

test('issue 650', () => {
  expect(Object.keys(mergeDeepRight({ a : () => {} }, { b : () => {} }))).toEqual([
    'a',
    'b',
  ])
})

test('ramda compatible test 1', () => {
  const a = {
    w : 1,
    x : 2,
    y : { z : 3 },
  }
  const b = {
    a : 4,
    b : 5,
    c : { d : 6 },
  }
  const result = mergeDeepRight(a, b)
  const expected = {
    w : 1,
    x : 2,
    y : { z : 3 },
    a : 4,
    b : 5,
    c : { d : 6 },
  }

  expect(result).toEqual(expected)
})

test('ramda compatible test 2', () => {
  const a = {
    a : {
      b : 1,
      c : 2,
    },
    y : 0,
  }
  const b = {
    a : {
      b : 3,
      d : 4,
    },
    z : 0,
  }
  const result = mergeDeepRight(a, b)
  const expected = {
    a : {
      b : 3,
      c : 2,
      d : 4,
    },
    y : 0,
    z : 0,
  }

  expect(result).toEqual(expected)
})

test('ramda compatible test 3', () => {
  const a = {
    w : 1,
    x : { y : 2 },
  }
  const result = mergeDeepRight(a, { x : { y : 3 } })
  const expected = {
    w : 1,
    x : { y : 3 },
  }
  expect(result).toEqual(expected)
})

test('functions are not discarded', () => {
  const obj = { foo : () => {} }
  expect(typeof mergeDeepRight(obj, {}).foo).toBe('function')
})

import {mergeDeepRight} from 'rambda'

interface Output {
  foo: {
    bar: number,
  },
}

describe('R.mergeDeepRight', () => {
  const result = mergeDeepRight<Output>({foo: {bar: 1}}, {foo: {bar: 2}})
  result.foo.bar // $ExpectType number
})

mergeLeft

mergeLeft<Output>(newProps: object, target: object): Output

Same as R.merge, but in opposite direction.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.mergeLeft(%0A%20%20%7Ba%3A%2010%7D%2C%0A%20%20%7Ba%3A%201%2C%20b%3A%202%7D%0A)%0A%2F%2F%20%3D%3E%20%7Ba%3A10%2C%20b%3A%202%7D">Try this <strong>R.mergeLeft</strong> example in Rambda REPL</a>

mergeLeft<Output>(newProps: object, target: object): Output;
mergeLeft<Output>(newProps: object): (target: object) => Output;

import { mergeRight } from './mergeRight.js'

export function mergeLeft(x, y){
  if (arguments.length === 1) return _y => mergeLeft(x, _y)

  return mergeRight(y, x)
}

import { mergeLeft } from './mergeLeft.js'

const obj = {
  foo : 1,
  bar : 2,
}

test('happy', () => {
  expect(mergeLeft({ bar : 20 }, obj)).toEqual({
    foo : 1,
    bar : 20,
  })
})

test('curry', () => {
  expect(mergeLeft({ baz : 3 })(obj)).toEqual({
    foo : 1,
    bar : 2,
    baz : 3,
  })
})

test('when undefined or null instead of object', () => {
  expect(mergeLeft(null, undefined)).toEqual({})
  expect(mergeLeft(obj, null)).toEqual(obj)
  expect(mergeLeft(obj, undefined)).toEqual(obj)
  expect(mergeLeft(undefined, obj)).toEqual(obj)
})

import {mergeLeft} from 'rambda'

interface Output {
  foo: number,
  bar: number,
}

describe('R.mergeLeft', () => {
  const result = mergeLeft<Output>({foo: 1}, {bar: 2})
  const curriedResult = mergeLeft<Output>({foo: 1})({bar: 2})

  result.foo // $ExpectType number
  result.bar // $ExpectType number
  curriedResult.bar // $ExpectType number
})

mergeRight

It creates a copy of target object with overwritten newProps properties. Previously known as R.merge but renamed after Ramda did the same.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20target%20%3D%20%7B%20'foo'%3A%200%2C%20'bar'%3A%201%20%7D%0Aconst%20newProps%20%3D%20%7B%20'foo'%3A%207%20%7D%0A%0Aconst%20result%20%3D%20R.mergeRight(target%2C%20newProps)%0A%2F%2F%20%3D%3E%20%7B%20'foo'%3A%207%2C%20'bar'%3A%201%20%7D">Try this <strong>R.mergeRight</strong> example in Rambda REPL</a>

mergeWith

mergeWith(fn: (x: any, z: any) => any, a: Record<string, unknown>, b: Record<string, unknown>): Record<string, unknown>

It takes two objects and a function, which will be used when there is an overlap between the keys.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.mergeWith(%0A%20%20R.concat%2C%0A%20%20%7Bvalues%20%3A%20%5B%2010%2C%2020%20%5D%7D%2C%0A%20%20%7Bvalues%20%3A%20%5B%2015%2C%2035%20%5D%7D%0A)%0A%2F%2F%20%3D%3E%20%5B%2010%2C%2020%2C%2015%2C%2035%20%5D">Try this <strong>R.mergeWith</strong> example in Rambda REPL</a>

mergeWith(fn: (x: any, z: any) => any, a: Record<string, unknown>, b: Record<string, unknown>): Record<string, unknown>;
mergeWith<Output>(fn: (x: any, z: any) => any, a: Record<string, unknown>, b: Record<string, unknown>): Output;
mergeWith(fn: (x: any, z: any) => any, a: Record<string, unknown>): (b: Record<string, unknown>) => Record<string, unknown>;
mergeWith<Output>(fn: (x: any, z: any) => any, a: Record<string, unknown>): (b: Record<string, unknown>) => Output;
mergeWith(fn: (x: any, z: any) => any): <U, V>(a: U, b: V) => Record<string, unknown>;
mergeWith<Output>(fn: (x: any, z: any) => any): <U, V>(a: U, b: V) => Output;

import { curry } from './curry.js'

export function mergeWithFn(
  mergeFn, aInput, bInput
){
  const a = aInput ?? {}
  const b = bInput ?? {}
  const willReturn = {}

  Object.keys(a).forEach(key => {
    if (b[ key ] === undefined) willReturn[ key ] = a[ key ]
    else willReturn[ key ] = mergeFn(a[ key ], b[ key ])
  })

  Object.keys(b).forEach(key => {
    if (willReturn[ key ] !== undefined) return

    if (a[ key ] === undefined) willReturn[ key ] = b[ key ]
    else willReturn[ key ] = mergeFn(a[ key ], b[ key ])
  })

  return willReturn
}

export const mergeWith = curry(mergeWithFn)

import { concat } from './concat.js'
import { mergeWithFn } from './mergeWith.js'

test('happy', () => {
  const result = mergeWithFn(
    concat,
    {
      a      : true,
      values : [ 10, 20 ],
    },
    {
      b      : true,
      values : [ 15, 35 ],
    }
  )
  const expected = {
    a      : true,
    b      : true,
    values : [ 10, 20, 15, 35 ],
  }
  expect(result).toEqual(expected)
})

// https://github.com/ramda/ramda/pull/3222/files#diff-d925d9188b478d2f1d4b26012c6dddac374f9e9d7a336604d654b9a113bfc857
describe('acts as if nil values are simply empty objects', () => {
  it('if the first object is nil and the second empty', () => {
    expect(mergeWithFn(
      concat, undefined, {}
    )).toEqual({})
  })

  it('if the first object is empty and the second nil', () => {
    expect(mergeWithFn(
      concat, {}, null
    )).toEqual({})
  })

  it('if both objects are nil', () => {
    expect(mergeWithFn(
      concat, undefined, null
    )).toEqual({})
  })

  it('if the first object is not empty and the second is nil', () => {
    expect(mergeWithFn(
      concat, { a : 'a' }, null
    )).toEqual({ a : 'a' })
  })

  it('if the first object is nil and the second is not empty', () => {
    expect(mergeWithFn(
      concat, undefined, { a : 'a' }
    )).toEqual({ a : 'a' })
  })
})

import {concat, mergeWith} from 'rambda'

interface Output {
  a: boolean,
  b: boolean,
  values: number[],
}
const A = {
  a: true,
  values: [10, 20],
}
const B = {
  b: true,
  values: [15, 35],
}

describe('R.mergeWith', () => {
  test('no curry | without explicit types', () => {
    const result = mergeWith(concat, A, B)
    result // $ExpectType Record<string, unknown>
  })
  test('no curry | with explicit types', () => {
    const result = mergeWith<Output>(concat, A, B)
    result // $ExpectType Output
  })
  test('curry 1 | without explicit types', () => {
    const result = mergeWith(concat, A)(B)
    result // $ExpectType Record<string, unknown>
  })
  test('curry 1 | with explicit types', () => {
    const result = mergeWith<Output>(concat, A)(B)
    result // $ExpectType Output
  })
  test('curry 2 | without explicit types', () => {
    const result = mergeWith(concat)(A, B)
    result // $ExpectType Record<string, unknown>
  })
  test('curry 2 | with explicit types', () => {
    const result = mergeWith<Output>(concat)(A, B)
    result // $ExpectType Output
  })
})

min

It returns the lesser value between x and y.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.min(5%2C%207)%2C%20%20%0A%20%20R.min('bar'%2C%20'foo')%2C%20%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B5%2C%20'bar'%5D">Try this <strong>R.min</strong> example in Rambda REPL</a>

minBy

It returns the lesser value between x and y according to compareFn function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20compareFn%20%3D%20Math.abs%0A%0Aconst%20result%20%3D%20R.minBy(compareFn%2C%20-5%2C%202)%20%2F%2F%20%3D%3E%20-5">Try this <strong>R.minBy</strong> example in Rambda REPL</a>

modify

modify<K extends PropertyKey, T>(prop: K, fn: (value: T) => T): <U extends Record<K, T>>(object: U) => U

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.modify()%0A%2F%2F%20%3D%3E">Try this <strong>R.modify</strong> example in Rambda REPL</a>

modify<K extends PropertyKey, T>(prop: K, fn: (value: T) => T): <U extends Record<K, T>>(object: U) => U;
modify<U, K extends keyof U>(prop: K, fn: (value: U[K]) => U[K], object: U): U;
modify<K extends PropertyKey>(prop: K): {
  <T>(fn: (value: T) => T): <U extends Record<K, T>>(object: U) => U;
  <T, U extends Record<K, T>>(fn: (value: T) => T, object: U): U;
};

import { isArray } from './_internals/isArray.js'
import { isIterable } from './_internals/isIterable.js'
import { curry } from './curry.js'
import { updateFn } from './update.js'

function modifyFn(
  property, fn, iterable
){
  if (!isIterable(iterable)) return iterable
  if (iterable[ property ] === undefined) return iterable
  if (isArray(iterable)){
    return updateFn(
      property, fn(iterable[ property ]), iterable
    )
  }

  return {
    ...iterable,
    [ property ] : fn(iterable[ property ]),
  }
}

export const modify = curry(modifyFn)

import { modify as modifyRamda } from 'ramda'

import { compareCombinations, FALSY_VALUES } from './_internals/testUtils.js'
import { add } from './add.js'
import { compose } from './compose.js'
import { modify } from './modify.js'

const person = {
  name : 'foo',
  age  : 20,
}

test('happy', () => {
  expect(modify(
    'age', x => x + 1, person
  )).toEqual({
    name : 'foo',
    age  : 21,
  })
})

test('property is missing', () => {
  expect(modify(
    'foo', x => x + 1, person
  )).toEqual(person)
})

test('adjust if `array` at the given key with the `transformation` function', () => {
  expect(modify(
    1, add(1), [ 100, 1400 ]
  )).toEqual([ 100, 1401 ])
})

describe('ignores transformations if the input value is not Array and Object', () => {
  ;[ 42, undefined, null, '' ].forEach(value => {
    it(`${ value }`, () => {
      expect(modify(
        'a', add(1), value
      )).toEqual(value)
    })
  })
})

const possibleProperties = [ ...FALSY_VALUES, 'foo', 0 ]
const possibleTransformers = [
  ...FALSY_VALUES,
  add(1),
  add('foo'),
  compose,
  String,
]
const possibleObjects = [
  ...FALSY_VALUES,
  {},
  [ 1, 2, 3 ],
  {
    a   : 1,
    foo : 2,
  },
  {
    a   : 1,
    foo : [ 1 ],
  },
  {
    a   : 1,
    foo : 'bar',
  },
]

describe('brute force', () => {
  compareCombinations({
    fn          : modify,
    fnRamda     : modifyRamda,
    firstInput  : possibleProperties,
    secondInput : possibleTransformers,
    thirdInput  : possibleObjects,
    callback    : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
        {
          "ERRORS_MESSAGE_MISMATCH": 0,
          "ERRORS_TYPE_MISMATCH": 0,
          "RESULTS_MISMATCH": 0,
          "SHOULD_NOT_THROW": 0,
          "SHOULD_THROW": 0,
          "TOTAL_TESTS": 630,
        }
      `)
    },
  })
})

import { add, identity, map, modify, pipe, toUpper } from 'rambda';

type Obj = {
	foo: string;
	bar: number;
};

describe('R.modify', () => {
	it('ramda tests', () => {
		const result1 = modify('foo', toUpper, {} as Obj);
		result1; // $ExpectType Obj

		const result2 = modify('bar', add(1), {} as Obj);
		result2; // $ExpectType Obj

		const result3 = modify('foo', toUpper)({} as Obj);
		result3; // $ExpectType Obj

		const result4 = modify('bar', add(1))({} as Obj);
		result4; // $ExpectType Obj

		const result5 = modify('foo')(toUpper)({} as Obj);
		result5; // $ExpectType Obj

		const result6 = modify('bar')(add(1))({} as Obj);
		result6; // $ExpectType Obj

		const result7 = modify('foo')(toUpper, {} as Obj);
		result7; // $ExpectType Obj

		const result8 = modify('bar')(add(1), {} as Obj);
		result8; // $ExpectType Obj

		const result9 = modify('foo', identity, {} as Obj);
		result9; // $ExpectType Obj

		// @ts-expect-error
		modify('foo', add(1), {} as Obj);
		// @ts-expect-error
		modify('bar', toUpper, {} as Obj);

		const f = pipe(map<Obj, Obj>(modify('foo', toUpper)));

		f([] as Obj[]); // $ExpectType Obj[]
	});
});

modifyPath

It changes a property of object on the base of provided path and transformer function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.modifyPath('a.b.c'%2C%20x%3D%3E%20x%2B1%2C%20%7Ba%3A%7Bb%3A%20%7Bc%3A1%7D%7D%7D)%0A%2F%2F%20%3D%3E%20%7Ba%3A%7Bb%3A%20%7Bc%3A2%7D%7D%7D">Try this <strong>R.modifyPath</strong> example in Rambda REPL</a>

modulo

Curried version of x%y.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.modulo(17%2C%203)%20%2F%2F%20%3D%3E%202">Try this <strong>R.modulo</strong> example in Rambda REPL</a>

move

It returns a copy of list with exchanged fromIndex and toIndex elements.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%5D%0Aconst%20result%20%3D%20R.move(0%2C%201%2C%20list)%0A%2F%2F%20%3D%3E%20%5B2%2C%201%2C%203%5D">Try this <strong>R.move</strong> example in Rambda REPL</a>

multiply

Curried version of x*y.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.multiply(2%2C%204)%20%2F%2F%20%3D%3E%208">Try this <strong>R.multiply</strong> example in Rambda REPL</a>

negate

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.negate(420)%2F%2F%20%3D%3E%20-420">Try this <strong>R.negate</strong> example in Rambda REPL</a>

none

none<T>(predicate: (x: T) => boolean, list: T[]): boolean

It returns true, if all members of array list returns false, when applied as argument to predicate function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%200%2C%201%2C%202%2C%203%2C%204%20%5D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3E%206%0A%0Aconst%20result%20%3D%20R.none(predicate%2C%20arr)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.none</strong> example in Rambda REPL</a>

none<T>(predicate: (x: T) => boolean, list: T[]): boolean;
none<T>(predicate: (x: T) => boolean): (list: T[]) => boolean;

export function none(predicate, list){
  if (arguments.length === 1) return _list => none(predicate, _list)

  for (let i = 0; i < list.length; i++){
    if (predicate(list[ i ])) return false
  }

  return true
}

import { none } from './none.js'

const isEven = n => n % 2 === 0

test('when true', () => {
  expect(none(isEven, [ 1, 3, 5, 7 ])).toBeTrue()
})

test('when false curried', () => {
  expect(none(input => input > 1, [ 1, 2, 3 ])).toBeFalse()
})

import {none} from 'rambda'

describe('R.none', () => {
  it('happy', () => {
    const result = none(
      x => {
        x // $ExpectType number
        return x > 0
      },
      [1, 2, 3]
    )
    result // $ExpectType boolean
  })
  it('curried needs a type', () => {
    const result = none<number>(x => {
      x // $ExpectType number
      return x > 0
    })([1, 2, 3])
    result // $ExpectType boolean
  })
})

not

not(input: any): boolean

It returns a boolean negated version of input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.not(false)%20%2F%2F%20true">Try this <strong>R.not</strong> example in Rambda REPL</a>

not(input: any): boolean;

export function not(input){
  return !input
}

import { not } from './not.js'

test('not', () => {
  expect(not(false)).toBeTrue()
  expect(not(true)).toBeFalse()
  expect(not(0)).toBeTrue()
  expect(not(1)).toBeFalse()
})

import {not} from 'rambda'

describe('R.not', () => {
  it('happy', () => {
    const result = not(4)

    result // $ExpectType boolean
  })
})

nth

nth(index: number, input: string): string

Curried version of input[index].

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%5D%0Aconst%20str%20%3D%20'foo'%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.nth(2%2C%20list)%2C%0A%20%20R.nth(6%2C%20list)%2C%0A%20%20R.nth(0%2C%20str)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5B3%2C%20undefined%2C%20'f'%5D">Try this <strong>R.nth</strong> example in Rambda REPL</a>

nth(index: number, input: string): string;	
nth<T>(index: number, input: T[]): T | undefined;	
nth(n: number): {
  <T>(input: T[]): T | undefined;
  (input: string): string;
};

export function nth(index, input){
  if (arguments.length === 1) return _input => nth(index, _input)

  const idx = index < 0 ? input.length + index : index

  return Object.prototype.toString.call(input) === '[object String]' ?
    input.charAt(idx) :
    input[ idx ]
}

import { nth } from './nth.js'

test('happy', () => {
  expect(nth(2, [ 1, 2, 3, 4 ])).toBe(3)
})

test('with curry', () => {
  expect(nth(2)([ 1, 2, 3, 4 ])).toBe(3)
})

test('with string and correct index', () => {
  expect(nth(2)('foo')).toBe('o')
})

test('with string and invalid index', () => {
  expect(nth(20)('foo')).toBe('')
})

test('with negative index', () => {
  expect(nth(-3)([ 1, 2, 3, 4 ])).toBe(2)
})

import {nth} from 'rambda'

const list = [1, 2, 3]

describe('R.nth', () => {
  it('happy', () => {
    const result = nth(4, list)

    result // $ExpectType number | undefined
  })
  it('curried', () => {
    const result = nth(1)(list)

    result // $ExpectType number | undefined
  })
})

describe('R.nth - string', () => {
  const str = 'abc'
  it('happy', () => {
    const result = nth(4, str)

    result // $ExpectType string
  })
  it('curried', () => {
    const result = nth(1)(str)

    result // $ExpectType string
  })
})

objOf

It creates an object with a single key-value pair.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.objOf('foo'%2C%20'bar')%0A%2F%2F%20%3D%3E%20%7Bfoo%3A%20'bar'%7D">Try this <strong>R.objOf</strong> example in Rambda REPL</a>

of

of<T>(x: T): T[]

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.of(null)%3B%20%2F%2F%20%3D%3E%20%5Bnull%5D%0Aconst%20result%20%3D%20R.of(%5B42%5D)%3B%20%2F%2F%20%3D%3E%20%5B%5B42%5D%5D">Try this <strong>R.of</strong> example in Rambda REPL</a>

of<T>(x: T): T[];

export function of(value){
  return [ value ]
}

import { of } from './of.js'

test('happy', () => {
  expect(of(3)).toEqual([ 3 ])

  expect(of(null)).toEqual([ null ])
})

import {of} from 'rambda'

const list = [1, 2, 3]

describe('R.of', () => {
  it('happy', () => {
    const result = of(4)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = of(list)

    result // $ExpectType number[][]
  })
})

omit

omit<T, K extends string>(propsToOmit: K[], obj: T): Omit<T, K>

It returns a partial copy of an obj without propsToOmit properties.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A%201%2C%20b%3A%202%2C%20c%3A%203%7D%0Aconst%20propsToOmit%20%3D%20'a%2Cc%2Cd'%0Aconst%20propsToOmitList%20%3D%20%5B'a'%2C%20'c'%2C%20'd'%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.omit(propsToOmit%2C%20Record%3Cstring%2C%20unknown%3E)%2C%20%0A%20%20R.omit(propsToOmitList%2C%20Record%3Cstring%2C%20unknown%3E)%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B%7Bb%3A%202%7D%2C%20%7Bb%3A%202%7D%5D">Try this <strong>R.omit</strong> example in Rambda REPL</a>

omit<T, K extends string>(propsToOmit: K[], obj: T): Omit<T, K>;
omit<K extends string>(propsToOmit: K[]): <T>(obj: T) => Omit<T, K>;
omit<T, U>(propsToOmit: string, obj: T): U;
omit<T, U>(propsToOmit: string): (obj: T) => U;
omit<T>(propsToOmit: string, obj: object): T;
omit<T>(propsToOmit: string): (obj: object) => T;

import { createPath } from './_internals/createPath.js'
import { includes } from './_internals/includes.js'

export function omit(propsToOmit, obj){
  if (arguments.length === 1) return _obj => omit(propsToOmit, _obj)

  if (obj === null || obj === undefined)
    return undefined

  const propsToOmitValue = createPath(propsToOmit, ',')
  const willReturn = {}

  for (const key in obj)
    if (!includes(key, propsToOmitValue))
      willReturn[ key ] = obj[ key ]

  return willReturn
}

import { omit } from './omit.js'

test('with string as condition', () => {
  const obj = {
    a : 1,
    b : 2,
    c : 3,
  }
  const result = omit('a,c', obj)
  const resultCurry = omit('a,c')(obj)
  const expectedResult = { b : 2 }

  expect(result).toEqual(expectedResult)
  expect(resultCurry).toEqual(expectedResult)
})

test.only('with number as property to omit', () => {
  const obj = {
    1 : 1,
    b : 2,
  }
  const result = omit([ 1 ], obj)
  expect(result).toEqual({ b : 2 })
})

test('with null', () => {
  expect(omit('a,b', null)).toBeUndefined()
})

test('happy', () => {
  expect(omit([ 'a', 'c' ])({
    a : 'foo',
    b : 'bar',
    c : 'baz',
  })).toEqual({ b : 'bar' })
})

import {omit} from 'rambda'

describe('R.omit with array as props input', () => {
  it('allow Typescript to infer object type', () => {
    const input = {a: 'foo', b: 2, c: 3, d: 4}
    const result = omit(['b,c'], input)

    result.a // $ExpectType string
    result.d // $ExpectType number

    const curriedResult = omit(['a,c'], input)

    curriedResult.a // $ExpectType string
    curriedResult.d // $ExpectType number
  })

  it('declare type of input object', () => {
    interface Input {
      a: string,
      b: number,
      c: number,
      d: number,
    }
    const input: Input = {a: 'foo', b: 2, c: 3, d: 4}
    const result = omit(['b,c'], input)
    result // $ExpectType Omit<Input, "b,c">

    result.a // $ExpectType string
    result.d // $ExpectType number

    const curriedResult = omit(['a,c'], input)

    curriedResult.a // $ExpectType string
    curriedResult.d // $ExpectType number
  })
})

describe('R.omit with string as props input', () => {
  interface Output {
    b: number,
    d: number,
  }

  it('explicitly declare output', () => {
    const result = omit<Output>('a,c', {a: 1, b: 2, c: 3, d: 4})
    result // $ExpectType Output
    result.b // $ExpectType number

    const curriedResult = omit<Output>('a,c')({a: 1, b: 2, c: 3, d: 4})

    curriedResult.b // $ExpectType number
  })

  it('explicitly declare input and output', () => {
    interface Input {
      a: number,
      b: number,
      c: number,
      d: number,
    }
    const result = omit<Input, Output>('a,c', {a: 1, b: 2, c: 3, d: 4})
    result // $ExpectType Output
    result.b // $ExpectType number

    const curriedResult = omit<Input, Output>('a,c')({
      a: 1,
      b: 2,
      c: 3,
      d: 4,
    })

    curriedResult.b // $ExpectType number
  })

  it('without passing type', () => {
    const result = omit('a,c', {a: 1, b: 2, c: 3, d: 4})
    result // $ExpectType unknown
  })
})

on

It passes the two inputs through unaryFn and then the results are passed as inputs the the binaryFn to receive the final result(binaryFn(unaryFn(FIRST_INPUT), unaryFn(SECOND_INPUT))).

This method is also known as P combinator.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.on((a%2C%20b)%20%3D%3E%20a%20%2B%20b%2C%20R.prop('a')%2C%20%7Bb%3A0%2C%20a%3A1%7D%2C%20%7Ba%3A2%7D)%0A%2F%2F%20%3D%3E%203">Try this <strong>R.on</strong> example in Rambda REPL</a>

once

once<T extends AnyFunction, C = unknown>(fn: T, context?: C): T

It returns a function, which invokes only once fn function.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?let%20result%20%3D%200%0Aconst%20addOnce%20%3D%20R.once((x)%20%3D%3E%20result%20%3D%20result%20%2B%20x)%0A%0AaddOnce(1)%0Aconst%20result%20%3D%20addOnce(1)%0A%2F%2F%20%3D%3E%201">Try this <strong>R.once</strong> example in Rambda REPL</a>

once<T extends AnyFunction, C = unknown>(fn: T, context?: C): T;

import { curry } from './curry.js'

function onceFn(fn, context){
  let result

  return function (){
    if (fn){
      result = fn.apply(context || this, arguments)
      fn = null
    }

    return result
  }
}

export function once(fn, context){
  if (arguments.length === 1){
    const wrap = onceFn(fn, context)

    return curry(wrap)
  }

  return onceFn(fn, context)
}

import { once } from './once.js'

test('with counter', () => {
  let counter = 0
  const runOnce = once(x => {
    counter++

    return x + 2
  })
  expect(runOnce(1)).toBe(3)
  runOnce(1)
  runOnce(1)
  runOnce(1)
  expect(counter).toBe(1)
})

test('happy path', () => {
  const addOneOnce = once((
    a, b, c
  ) => a + b + c, 1)

  expect(addOneOnce(
    10, 20, 30
  )).toBe(60)
  expect(addOneOnce(40)).toBe(60)
})

test('with context', () => {
  const context = { name: 'fris' }
  const getNameOnce = once(function (){
    return this.name
  }, context)

  expect(getNameOnce()).toBe('fris')
  expect(getNameOnce()).toBe('fris')
  expect(getNameOnce()).toBe('fris')
})

import {once} from 'rambda'

describe('R.once', () => {
  it('happy', () => {
    const runOnce = once((x: number) => {
      return x + 2
    })

    const result = runOnce(1)
    result // $ExpectType number
  })
  it('with context', () => {
    const runOnce = once(function (this: any, x: number) {
      return x + 2
    })

    const result = runOnce.call({}, 1)
    result // $ExpectType number
  })
})

or

Logical OR

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?R.or(false%2C%20true)%3B%20%2F%2F%20%3D%3E%20true%0AR.or(false%2C%20false)%3B%20%2F%2F%20%3D%3E%20false%0Aconst%20result%20%3D%20R.or(false%2C%20'foo')%3B%20%2F%2F%20%3D%3E%20'foo'">Try this <strong>R.or</strong> example in Rambda REPL</a>

over

over<S, A>(lens: Lens<S, A>): {
  (fn: (a: A) => A): (value: S) => S

It returns a copied Object or Array with modified value received by applying function fn to lens focus.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20headLens%20%3D%20R.lensIndex(0)%0A%20%0Aconst%20result%20%3D%20R.over(headLens%2C%20R.toUpper%2C%20%5B'foo'%2C%20'bar'%2C%20'baz'%5D)%20%2F%2F%20%3D%3E%20%5B'FOO'%2C%20'bar'%2C%20'baz'%5D">Try this <strong>R.over</strong> example in Rambda REPL</a>

over<S, A>(lens: Lens<S, A>): {
  (fn: (a: A) => A): (value: S) => S;
  (fn: (a: A) => A, value: S): S;
};
over<S, A>(lens: Lens<S, A>, fn: (a: A) => A): (value: S) => S;
over<S, A>(lens: Lens<S, A>, fn: (a: A) => A, value: S): S;

import { curry } from './curry.js'

const Identity = x => ({
  x,
  map : fn => Identity(fn(x)),
})

function overFn(
  lens, fn, object
){
  return lens(x => Identity(fn(x)))(object).x
}

export const over = curry(overFn)

import { assoc } from './assoc.js'
import { lens } from './lens.js'
import { lensIndex } from './lensIndex.js'
import { lensPath } from './lensPath.js'
import { over } from './over.js'
import { prop } from './prop.js'
import { toUpper } from './toUpper.js'

const testObject = {
  foo : 'bar',
  baz : {
    a : 'x',
    b : 'y',
  },
}

test('assoc lens', () => {
  const assocLens = lens(prop('foo'), assoc('foo'))
  const result = over(
    assocLens, toUpper, testObject
  )
  const expected = {
    ...testObject,
    foo : 'BAR',
  }
  expect(result).toEqual(expected)
})

test('path lens', () => {
  const pathLens = lensPath('baz.a')
  const result = over(
    pathLens, toUpper, testObject
  )
  const expected = {
    ...testObject,
    baz : {
      a : 'X',
      b : 'y',
    },
  }
  expect(result).toEqual(expected)
})

test('index lens', () => {
  const indexLens = lensIndex(0)
  const result = over(indexLens, toUpper)([ 'foo', 'bar' ])
  expect(result).toEqual([ 'FOO', 'bar' ])
})

partial

partial<V0, V1, T>(fn: (x0: V0, x1: V1) => T, args: [V0]): (x1: V1) => T

It is very similar to R.curry, but you can pass initial arguments when you create the curried function.

R.partial will keep returning a function until all the arguments that the function fn expects are passed. The name comes from the fact that you partially inject the inputs.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20(title%2C%20firstName%2C%20lastName)%20%3D%3E%20%7B%0A%20%20return%20title%20%2B%20'%20'%20%2B%20firstName%20%2B%20'%20'%20%2B%20lastName%20%2B%20'!'%0A%7D%0A%0Aconst%20canPassAnyNumberOfArguments%20%3D%20R.partial(fn%2C%20'Hello')%0Aconst%20ramdaStyle%20%3D%20R.partial(fn%2C%20%5B'Hello'%5D)%0A%0Aconst%20finalFn%20%3D%20canPassAnyNumberOfArguments('Foo')%0A%0Aconst%20result%20%3D%20finalFn('Bar')%20%2F%2F%20%3D%3E%20%20'Hello%2C%20Foo%20Bar!'">Try this <strong>R.partial</strong> example in Rambda REPL</a>

partial<V0, V1, T>(fn: (x0: V0, x1: V1) => T, args: [V0]): (x1: V1) => T;
partial<V0, V1, V2, T>(fn: (x0: V0, x1: V1, x2: V2) => T, args: [V0, V1]): (x2: V2) => T;
partial<V0, V1, V2, T>(fn: (x0: V0, x1: V1, x2: V2) => T, args: [V0]): (x1: V1, x2: V2) => T;
partial<V0, V1, V2, V3, T>(
  fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T,
  args: [V0, V1, V2],
): (x2: V3) => T;
partial<V0, V1, V2, V3, T>(
  fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T,
  args: [V0, V1],
): (x2: V2, x3: V3) => T;
partial<V0, V1, V2, V3, T>(
  fn: (x0: V0, x1: V1, x2: V2, x3: V3) => T,
  args: [V0],
): (x1: V1, x2: V2, x3: V3) => T;
partial<T>(fn: (...a: any[]) => T, args: any[]): (...a: any[]) => T;

import { isArray } from './_internals/isArray.js'

export function partial(fn, ...args){
  const len = fn.length

  // If a single array argument is given, those are the args (a la Ramda).
  // Otherwise, the variadic arguments are the args.
  const argList = args.length === 1 && isArray(args[0]) ? args[0] : args

  return (...rest) => {
    if (argList.length + rest.length >= len){
      return fn(...argList, ...rest)
    }

    return partial(fn, ...[ ...argList, ...rest ])
  }
}

import { partial } from './partial.js'
import { type } from './type.js'

const greet = (
  salutation, title, firstName, lastName
) =>
  [salutation, title, firstName, lastName]

test('happy', () => {
  const canPassAnyNumberOfArguments = partial(
    greet, 'Hello', 'Ms.'
  )
  const fn = canPassAnyNumberOfArguments('foo')
  const sayHello = partial(greet, [ 'Hello' ])
  const sayHelloRamda = partial(sayHello, [ 'Ms.' ])

  expect(type(fn)).toBe('Function')

  expect(fn('bar')).toStrictEqual(['Hello', 'Ms.', 'foo', 'bar'])
  expect(sayHelloRamda('foo', 'bar')).toStrictEqual(['Hello', 'Ms.', 'foo', 'bar'])
})

test('extra arguments are ignored', () => {
  const canPassAnyNumberOfArguments = partial(
    greet, 'Hello', 'Ms.'
  )
  const fn = canPassAnyNumberOfArguments('foo')

  expect(type(fn)).toBe('Function')

  expect(fn(
    'bar', 1, 2
  )).toStrictEqual(['Hello', 'Ms.', 'foo', 'bar'])
})

test('when array is input', () => {
  const fooFn = (
    a, b, c, d
  ) => ({
    a,
    b,
    c,
    d,
  })
  const barFn = partial(
    fooFn, [ 1, 2 ], []
  )

  expect(barFn(1, 2)).toEqual({
    a : [ 1, 2 ],
    b : [],
    c : 1,
    d : 2,
  })
})

test('ramda spec', () => {
  const sayHello = partial(greet, 'Hello')
  const sayHelloToMs = partial(sayHello, 'Ms.')

  expect(sayHelloToMs('Jane', 'Jones')).toStrictEqual(['Hello', 'Ms.', 'Jane', 'Jones'])
})

import {partial} from 'rambda'

describe('R.partial', () => {
  it('happy', () => {
    function fn(
      aString: string,
      aNumber: number,
      aBoolean: boolean,
      aNull: null
    ) {
      return {aString, aNumber, aBoolean, aNull}
    }

    // @ts-expect-error
    partial(fn, 1)

    const fn1 = partial(fn, ['a'])
    partial(fn1, ['b'])

    const fn2 = partial(fn1, [2])
    const result = fn2(true, null)
    result // $ExpectType { aString: string; aNumber: number; aBoolean: boolean; aNull: null; }
  })
})

partialObject

partialObject<Input, PartialInput, Output>(
  fn: (input: Input) => Output, 
  partialInput: PartialInput,
): (input: Pick<Input, Exclude<keyof Input, keyof PartialInput>>) => Output

R.partialObject is a curry helper designed specifically for functions accepting object as a single argument.

Initially the function knows only a part from the whole input object and then R.partialObject helps in preparing the function for the second part, when it receives the rest of the input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20(%7B%20a%2C%20b%2C%20c%20%7D)%20%3D%3E%20a%20%2B%20b%20%2B%20c%0Aconst%20curried%20%3D%20R.partialObject(fn%2C%20%7B%20a%20%3A%201%20%7D)%0Aconst%20result%20%3D%20curried(%7B%0A%20%20b%20%3A%202%2C%0A%20%20c%20%3A%203%2C%0A%7D)%0A%2F%2F%20%3D%3E%206">Try this <strong>R.partialObject</strong> example in Rambda REPL</a>

partialObject<Input, PartialInput, Output>(
  fn: (input: Input) => Output, 
  partialInput: PartialInput,
): (input: Pick<Input, Exclude<keyof Input, keyof PartialInput>>) => Output;

import { mergeDeepRight } from './mergeDeepRight.js'

export function partialObject(fn, input){
  return nextInput => fn(mergeDeepRight(nextInput, input))
}

import { delay } from './delay.js'
import { partialObject } from './partialObject.js'
import { type } from './type.js'

test('with plain function', () => {
  const fn = ({ a, b, c }) => a + b + c
  const curried = partialObject(fn, { a : 1 })

  expect(type(curried)).toBe('Function')
  expect(curried({
    b : 2,
    c : 3,
  })).toBe(6)
})

test('with function that throws an error', () => {
  const fn = ({ a, b, c }) => {
    throw new Error('foo')
  }
  const curried = partialObject(fn, { a : 1 })

  expect(type(curried)).toBe('Function')
  expect(() =>
    curried({
      b : 2,
      c : 3,
    })).toThrowErrorMatchingInlineSnapshot('"foo"')
})

test('with async', async () => {
  const fn = async ({ a, b, c }) => {
    await delay(100)

    return a + b + c
  }

  const curried = partialObject(fn, { a : 1 })

  const result = await curried({
    b : 2,
    c : 3,
  })

  expect(result).toBe(6)
})

test('async function throwing an error', async () => {
  const fn = async ({ a, b, c }) => {
    await delay(100)
    throw new Error('foo')
  }

  const curried = partialObject(fn, { a : 1 })

  try {
    await curried({
      b : 2,
      c : 3,
    })
    expect(true).toBeFalsy()
  } catch (e){
    expect(e.message).toBe('foo')
  }
})

import {partialObject, delay} from 'rambda'

describe('R.partialObject', () => {
  it('happy', () => {
    interface Input {
      a: number,
      b: number,
      c: string,
    }
    const fn = ({a, b, c}: Input) => a + b + c
    const curried = partialObject(fn, {a: 1})
    const result = curried({
      b: 2,
      c: 'foo',
    })
    result // $ExpectType string
  })
  it('asynchronous', async() => {
    interface Input {
      a: number,
      b: number,
      c: string,
    }
    const fn = async({a, b, c}: Input) => {
      await delay(100)
      return a + b + c
    }
    const curried = partialObject(fn, {a: 1})
    const result = await curried({
      b: 2,
      c: 'foo',
    })
    result // $ExpectType string
  })
})

partition

partition<T>(
  predicate: Predicate<T>,
  input: T[]
): [T[], T[]]

It will return array of two objects/arrays according to predicate function. The first member holds all instances of input that pass the predicate function, while the second member - those who doesn't.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%5D%0Aconst%20obj%20%3D%20%7Ba%3A%201%2C%20b%3A%202%2C%20c%3A%203%7D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3E%202%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.partition(predicate%2C%20list)%2C%0A%20%20R.partition(predicate%2C%20Record%3Cstring%2C%20unknown%3E)%0A%5D%0Aconst%20expected%20%3D%20%5B%0A%20%20%5B%5B3%5D%2C%20%5B1%2C%202%5D%5D%2C%0A%20%20%5B%7Bc%3A%203%7D%2C%20%20%7Ba%3A%201%2C%20b%3A%202%7D%5D%2C%0A%5D%0A%2F%2F%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.partition</strong> example in Rambda REPL</a>

partition<T>(
  predicate: Predicate<T>,
  input: T[]
): [T[], T[]];
partition<T>(
  predicate: Predicate<T>
): (input: T[]) => [T[], T[]];
partition<T>(
  predicate: (x: T, prop?: string) => boolean,
  input: { [key: string]: T}
): [{ [key: string]: T}, { [key: string]: T}];
partition<T>(
  predicate: (x: T, prop?: string) => boolean
): (input: { [key: string]: T}) => [{ [key: string]: T}, { [key: string]: T}];

import { isArray } from './_internals/isArray.js'

export function partitionObject(predicate, iterable){
  const yes = {}
  const no = {}
  Object.entries(iterable).forEach(([ prop, value ]) => {
    if (predicate(value, prop)){
      yes[ prop ] = value
    } else {
      no[ prop ] = value
    }
  })

  return [ yes, no ]
}

export function partitionArray(
  predicate, list, indexed = false
){
  const yes = []
  const no = []
  let counter = -1

  while (counter++ < list.length - 1){
    if (
      indexed ? predicate(list[ counter ], counter) : predicate(list[ counter ])
    ){
      yes.push(list[ counter ])
    } else {
      no.push(list[ counter ])
    }
  }

  return [ yes, no ]
}

export function partition(predicate, iterable){
  if (arguments.length === 1){
    return listHolder => partition(predicate, listHolder)
  }
  if (!isArray(iterable)) return partitionObject(predicate, iterable)

  return partitionArray(predicate, iterable)
}

import { partition } from './partition.js'

test('with array', () => {
  const predicate = x => x > 2
  const list = [ 1, 2, 3, 4 ]

  const result = partition(predicate, list)
  const expectedResult = [
    [ 3, 4 ],
    [ 1, 2 ],
  ]

  expect(result).toEqual(expectedResult)
})

test('with object', () => {
  const predicate = (value, prop) => {
    expect(typeof prop).toBe('string')

    return value > 2
  }
  const hash = {
    a : 1,
    b : 2,
    c : 3,
    d : 4,
  }

  const result = partition(predicate)(hash)
  const expectedResult = [
    {
      c : 3,
      d : 4,
    },
    {
      a : 1,
      b : 2,
    },
  ]

  expect(result).toEqual(expectedResult)
})

test('readme example', () => {
  const list = [ 1, 2, 3 ]
  const obj = {
    a : 1,
    b : 2,
    c : 3,
  }
  const predicate = x => x > 2

  const result = [ partition(predicate, list), partition(predicate, obj) ]
  const expected = [
    [ [ 3 ], [ 1, 2 ] ],
    [
      { c : 3 },
      {
        a : 1,
        b : 2,
      },
    ],
  ]
  expect(result).toEqual(expected)
})

import {partition} from 'rambda'

describe('R.partition', () => {
  it('with array', () => {
    const predicate = (x: number) => {
      return x > 2
    }
    const list = [1, 2, 3, 4]

    const result = partition(predicate, list)
    const curriedResult = partition(predicate)(list)
    result // $ExpectType [number[], number[]]
    curriedResult // $ExpectType [number[], number[]]
  })

  /*
    revert to old version of `dtslint` and `R.partition` typing
    as there is diff between VSCode types(correct) and dtslint(incorrect)
    
    it('with object', () => {
      const predicate = (value: number, prop?: string) => {
        return value > 2
      }
      const hash = {
        a: 1,
        b: 2,
        c: 3,
        d: 4,
      }
  
      const result = partition(predicate, hash)
      const curriedResult = partition(predicate)(hash)
      result[0] // $xExpectType { [key: string]: number; }
      result[1] // $xExpectType { [key: string]: number; }
      curriedResult[0] // $xExpectType { [key: string]: number; }
      curriedResult[1] // $xExpectType { [key: string]: number; }
    })
    */
})

path

path<S, K0 extends keyof S = keyof S>(path: [K0], obj: S): S[K0]

If pathToSearch is 'a.b' then it will return 1 if obj is {a:{b:1}}.

It will return undefined, if such path is not found.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A%20%7Bb%3A%201%7D%7D%0Aconst%20pathToSearch%20%3D%20'a.b'%0Aconst%20pathToSearchList%20%3D%20%5B'a'%2C%20'b'%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.path(pathToSearch%2C%20obj)%2C%0A%20%20R.path(pathToSearchList%2C%20obj)%2C%0A%20%20R.path('a.b.c.d'%2C%20obj)%0A%5D%0A%2F%2F%20%3D%3E%20%5B1%2C%201%2C%20undefined%5D">Try this <strong>R.path</strong> example in Rambda REPL</a>

path<S, K0 extends keyof S = keyof S>(path: [K0], obj: S): S[K0];
path<S, K0 extends keyof S = keyof S, K1 extends keyof S[K0] = keyof S[K0]>(path: [K0, K1], obj: S): S[K0][K1];
path<
    S,
    K0 extends keyof S = keyof S,
    K1 extends keyof S[K0] = keyof S[K0],
    K2 extends keyof S[K0][K1] = keyof S[K0][K1]
>(path: [K0, K1, K2], obj: S): S[K0][K1][K2];
path<
    S,
    K0 extends keyof S = keyof S,
    K1 extends keyof S[K0] = keyof S[K0],
    K2 extends keyof S[K0][K1] = keyof S[K0][K1],
    K3 extends keyof S[K0][K1][K2] = keyof S[K0][K1][K2],
>(path: [K0, K1, K2, K3], obj: S): S[K0][K1][K2][K3];
path<
    S,
    K0 extends keyof S = keyof S,
    K1 extends keyof S[K0] = keyof S[K0],
    K2 extends keyof S[K0][K1] = keyof S[K0][K1],
    K3 extends keyof S[K0][K1][K2] = keyof S[K0][K1][K2],
    K4 extends keyof S[K0][K1][K2][K3] = keyof S[K0][K1][K2][K3],
>(path: [K0, K1, K2, K3, K4], obj: S): S[K0][K1][K2][K3][K4];
path<
    S,
    K0 extends keyof S = keyof S,
    K1 extends keyof S[K0] = keyof S[K0],
    K2 extends keyof S[K0][K1] = keyof S[K0][K1],
    K3 extends keyof S[K0][K1][K2] = keyof S[K0][K1][K2],
    K4 extends keyof S[K0][K1][K2][K3] = keyof S[K0][K1][K2][K3],
    K5 extends keyof S[K0][K1][K2][K3][K4] = keyof S[K0][K1][K2][K3][K4],
>(path: [K0, K1, K2, K3, K4, K5], obj: S): S[K0][K1][K2][K3][K4][K5];
path<T>(pathToSearch: string, obj: any): T | undefined;
path<T>(pathToSearch: string): (obj: any) => T | undefined;
path<T>(pathToSearch: RamdaPath): (obj: any) => T | undefined;
path<T>(pathToSearch: RamdaPath, obj: any): T | undefined;

import { createPath } from './_internals/createPath.js'

export function pathFn(pathInput, obj){
  let willReturn = obj
  let counter = 0

  const pathArrValue = createPath(pathInput)

  while (counter < pathArrValue.length){
    if (willReturn === null || willReturn === undefined){
      return undefined
    }
    if (willReturn[ pathArrValue[ counter ] ] === null) return undefined

    willReturn = willReturn[ pathArrValue[ counter ] ]
    counter++
  }

  return willReturn
}

export function path(pathInput, obj){
  if (arguments.length === 1) return _obj => path(pathInput, _obj)

  if (obj === null || obj === undefined){
    return undefined
  }

  return pathFn(pathInput, obj)
}

import { path } from './path.js'

test('with array inside object', () => {
  const obj = { a : { b : [ 1, { c : 1 } ] } }

  expect(path('a.b.1.c', obj)).toBe(1)
})

test('works with undefined', () => {
  const obj = { a : { b : { c : 1 } } }

  expect(path('a.b.c.d.f', obj)).toBeUndefined()
  expect(path('foo.babaz', undefined)).toBeUndefined()
  expect(path('foo.babaz')(undefined)).toBeUndefined()
})

test('works with string instead of array', () => {
  expect(path('foo.bar.baz')({ foo : { bar : { baz : 'yes' } } })).toBe('yes')
})

test('path', () => {
  expect(path([ 'foo', 'bar', 'baz' ])({ foo : { bar : { baz : 'yes' } } })).toBe('yes')
  expect(path([ 'foo', 'bar', 'baz' ])(null)).toBeUndefined()
  expect(path([ 'foo', 'bar', 'baz' ])({ foo : { bar : 'baz' } })).toBeUndefined()
})

test('with number string in between', () => {
	expect(path(['a','1','b'], {a: [{b: 1}, {b: 2}]})).toBe(2)
})

test('null is not a valid path', () => {
  expect(path('audio_tracks', {
    a            : 1,
    audio_tracks : null,
  })).toBeUndefined()
})

import {path} from 'rambda'

const input = {a: {b: {c: true}}}

describe('R.path with string as path', () => {
  it('without specified output type', () => {
    // $ExpectType unknown
    path('a.b.c', input)
    // $ExpectType unknown
    path('a.b.c')(input)
  })
  it('with specified output type', () => {
    // $ExpectType boolean | undefined
    path<boolean>('a.b.c', input)
    // $ExpectType boolean | undefined
    path<boolean>('a.b.c')(input)
  })
})

describe('R.path with list as path', () => {
  it('with array as path', () => {
    // $ExpectType boolean
    path(['a', 'b', 'c'], input)
    // $ExpectType unknown
    path(['a', 'b', 'c'])(input)
  })
  test('shallow property', () => {
    // $ExpectType number
    path(['a'], {a: 1})

    // $ExpectType unknown
    path(['b'], {a: 1})
  })
  test('deep property', () => {
    const testObject = {a: {b: {c: {d: {e: {f: 1}}}}}}
    const result = path(['a', 'b', 'c', 'd', 'e', 'f'], testObject)
    // $ExpectType number
    result
    const curriedResult = path(['a', 'b', 'c', 'd', 'e', 'f'])(testObject)
    // $ExpectType unknown
    curriedResult
  })
  test('issue #668 - path is not correct', () => {
    const object = {
      is: {
        a: 'path',
      },
    }
    const result = path(['is', 'not', 'a'], object)
    // $ExpectType unknown
    result
    const curriedResult = path(['is', 'not', 'a'])(object)
    // $ExpectType unknown
    curriedResult
  })
})

pathEq

pathEq(pathToSearch: Path, target: any, input: any): boolean

It returns true if pathToSearch of input object is equal to target value.

pathToSearch is passed to R.path, which means that it can be either a string or an array. Also equality between target and the found value is determined by R.equals.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20path%20%3D%20'a.b'%0Aconst%20target%20%3D%20%7Bc%3A%201%7D%0Aconst%20input%20%3D%20%7Ba%3A%20%7Bb%3A%20%7Bc%3A%201%7D%7D%7D%0A%0Aconst%20result%20%3D%20R.pathEq(%0A%20%20path%2C%0A%20%20target%2C%0A%20%20input%0A)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.pathEq</strong> example in Rambda REPL</a>

pathEq(pathToSearch: Path, target: any, input: any): boolean;
pathEq(pathToSearch: Path, target: any): (input: any) => boolean;
pathEq(pathToSearch: Path): (target: any) => (input: any) => boolean;

import { curry } from './curry.js'
import { equals } from './equals.js'
import { path } from './path.js'

function pathEqFn(
  pathToSearch, target, input
){
  return equals(path(pathToSearch, input), target)
}

export const pathEq = curry(pathEqFn)

import { pathEq } from './pathEq.js'

test('when true', () => {
  const path = 'a.b'
  const obj = { a : { b : { c : 1 } } }
  const target = { c : 1 }

  expect(pathEq(
    path, target, obj
  )).toBeTrue()
})

test('when false', () => {
  const path = 'a.b'
  const obj = { a : { b : 1 } }
  const target = 2

  expect(pathEq(path, target)(obj)).toBeFalse()
})

test('when wrong path', () => {
  const path = 'foo.bar'
  const obj = { a : { b : 1 } }
  const target = 2

  expect(pathEq(
    path, target, obj
  )).toBeFalse()
})

import {pathEq} from 'rambda'

describe('R.pathEq', () => {
  it('with string path', () => {
    const pathToSearch = 'a.b.c'
    const input = {a: {b: {c: 1}}}
    const target = {c: 1}

    const result = pathEq(pathToSearch, input, target)
    const curriedResult = pathEq(pathToSearch, input, target)
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })

  it('with array path', () => {
    const pathToSearch = ['a', 'b', 'c']
    const input = {a: {b: {c: 1}}}
    const target = {c: 1}

    const result = pathEq(pathToSearch, input, target)
    const curriedResult = pathEq(pathToSearch, input, target)
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
})

describe('with ramda specs', () => {
  const testPath = ['x', 0, 'y']
  const testObj = {
    x: [
      {y: 2, z: 3},
      {y: 4, z: 5},
    ],
  }

  const result1 = pathEq(testPath, 2, testObj)
  const result2 = pathEq(testPath, 2)(testObj)
  const result3 = pathEq(testPath)(2)(testObj)
  result1 // $ExpectType boolean
  result2 // $ExpectType boolean
  result3 // $ExpectType boolean
})

pathOr

pathOr<T>(defaultValue: T, pathToSearch: Path, obj: any): T

It reads obj input and returns either R.path(pathToSearch, Record<string, unknown>) result or defaultValue input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20defaultValue%20%3D%20'DEFAULT_VALUE'%0Aconst%20pathToSearch%20%3D%20'a.b'%0Aconst%20pathToSearchList%20%3D%20%5B'a'%2C%20'b'%5D%0A%0Aconst%20obj%20%3D%20%7B%0A%20%20a%20%3A%20%7B%0A%20%20%20%20b%20%3A%201%0A%20%20%7D%0A%7D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.pathOr(DEFAULT_VALUE%2C%20pathToSearch%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pathOr(DEFAULT_VALUE%2C%20pathToSearchList%2C%20Record%3Cstring%2C%20unknown%3E)%2C%20%0A%20%20R.pathOr(DEFAULT_VALUE%2C%20'a.b.c'%2C%20Record%3Cstring%2C%20unknown%3E)%0A%5D%0A%2F%2F%20%3D%3E%20%5B1%2C%201%2C%20'DEFAULT_VALUE'%5D">Try this <strong>R.pathOr</strong> example in Rambda REPL</a>

pathOr<T>(defaultValue: T, pathToSearch: Path, obj: any): T;
pathOr<T>(defaultValue: T, pathToSearch: Path): (obj: any) => T;
pathOr<T>(defaultValue: T): (pathToSearch: Path) => (obj: any) => T;

import { curry } from './curry.js'
import { defaultTo } from './defaultTo.js'
import { path } from './path.js'

function pathOrFn(
  defaultValue, pathInput, obj
){
  return defaultTo(defaultValue, path(pathInput, obj))
}

export const pathOr = curry(pathOrFn)

import { pathOr } from './pathOr.js'

test('with undefined', () => {
  const result = pathOr(
    'foo', 'x.y', { x : { y : 1 } }
  )

  expect(result).toBe(1)
})

test('with null', () => {
  const result = pathOr(
    'foo', 'x.y', null
  )

  expect(result).toBe('foo')
})

test('with NaN', () => {
  const result = pathOr(
    'foo', 'x.y', NaN
  )

  expect(result).toBe('foo')
})

test('curry case (x)(y)(z)', () => {
  const result = pathOr('foo')('x.y.z')({ x : { y : { a : 1 } } })

  expect(result).toBe('foo')
})

test('curry case (x)(y,z)', () => {
  const result = pathOr('foo', 'x.y.z')({ x : { y : { a : 1 } } })

  expect(result).toBe('foo')
})

test('curry case (x,y)(z)', () => {
  const result = pathOr('foo')('x.y.z', { x : { y : { a : 1 } } })

  expect(result).toBe('foo')
})

import {pathOr} from 'rambda'

describe('R.pathOr', () => {
  it('with string path', () => {
    const x = pathOr<string>('foo', 'x.y', {x: {y: 'bar'}})
    x // $ExpectType string
  })
  it('with array path', () => {
    const x = pathOr<string>('foo', ['x', 'y'], {x: {y: 'bar'}})
    x // $ExpectType string
  })
  it('without passing type looks bad', () => {
    const x = pathOr('foo', 'x.y', {x: {y: 'bar'}})
    x // $ExpectType "foo"
  })
  it('curried', () => {
    const x = pathOr<string>('foo', 'x.y')({x: {y: 'bar'}})
    x // $ExpectType string
  })
})

paths

paths<Input, T>(pathsToSearch: Path[], obj: Input): (T | undefined)[]

It loops over members of pathsToSearch as singlePath and returns the array produced by R.path(singlePath, Record<string, unknown>).

Because it calls R.path, then singlePath can be either string or a list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7B%0A%20%20a%20%3A%20%7B%0A%20%20%20%20b%20%3A%20%7B%0A%20%20%20%20%20%20c%20%3A%201%2C%0A%20%20%20%20%20%20d%20%3A%202%0A%20%20%20%20%7D%0A%20%20%7D%0A%7D%0A%0Aconst%20result%20%3D%20R.paths(%5B%0A%20%20'a.b.c'%2C%0A%20%20'a.b.d'%2C%0A%20%20'a.b.c.d.e'%2C%0A%5D%2C%20Record%3Cstring%2C%20unknown%3E)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%2C%20undefined%5D">Try this <strong>R.paths</strong> example in Rambda REPL</a>

paths<Input, T>(pathsToSearch: Path[], obj: Input): (T | undefined)[];
paths<Input, T>(pathsToSearch: Path[]): (obj: Input) => (T | undefined)[];
paths<T>(pathsToSearch: Path[], obj: any): (T | undefined)[];
paths<T>(pathsToSearch: Path[]): (obj: any) => (T | undefined)[];

import { path } from './path.js'

export function paths(pathsToSearch, obj){
  if (arguments.length === 1){
    return _obj => paths(pathsToSearch, _obj)
  }

  return pathsToSearch.map(singlePath => path(singlePath, obj))
}

import { paths } from './paths.js'

const obj = {
  a : {
    b : {
      c : 1,
      d : 2,
    },
  },
  p : [ { q : 3 } ],
  x : {
    y : 'FOO',
    z : [ [ {} ] ],
  },
}

test('with string path + curry', () => {
  const pathsInput = [ 'a.b.d', 'p.q' ]
  const expected = [ 2, undefined ]
  const result = paths(pathsInput, obj)
  const curriedResult = paths(pathsInput)(obj)

  expect(result).toEqual(expected)
  expect(curriedResult).toEqual(expected)
})

test('with array path', () => {
  const result = paths([
    [ 'a', 'b', 'c' ],
    [ 'x', 'y' ],
  ],
  obj)

  expect(result).toEqual([ 1, 'FOO' ])
})

test('takes a paths that contains indices into arrays', () => {
  expect(paths([
    [ 'p', 0, 'q' ],
    [ 'x', 'z', 0, 0 ],
  ],
  obj)).toEqual([ 3, {} ])
  expect(paths([
    [ 'p', 0, 'q' ],
    [ 'x', 'z', 2, 1 ],
  ],
  obj)).toEqual([ 3, undefined ])
})

test('gets a deep property\'s value from objects', () => {
  expect(paths([ [ 'a', 'b' ] ], obj)).toEqual([ obj.a.b ])
  expect(paths([ [ 'p', 0 ] ], obj)).toEqual([ obj.p[ 0 ] ])
})

test('returns undefined for items not found', () => {
  expect(paths([ [ 'a', 'x', 'y' ] ], obj)).toEqual([ undefined ])
  expect(paths([ [ 'p', 2 ] ], obj)).toEqual([ undefined ])
})

import {paths} from 'rambda'

interface Input {
  a: number,
  b: number,
  c: number,
}

const input: Input = {a: 1, b: 2, c: 3}

describe('R.paths', () => {
  it('with dot notation', () => {
    const result = paths<number>(['a.b.c', 'foo.bar'], input)
    result // $ExpectType (number | undefined)[]
  })

  it('without type', () => {
    const result = paths(['a.b.c', 'foo.bar'], input)
    result // $ExpectType unknown[]
  })

  it('with array as path', () => {
    const result = paths<number>([['a', 'b', 'c'], ['foo.bar']], input)
    result // $ExpectType (number | undefined)[]
  })

  it('curried', () => {
    const result = paths<number>([['a', 'b', 'c'], ['foo.bar']])(input)
    result // $ExpectType (number | undefined)[]
  })
})

pathSatisfies

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.pathSatisfies(%0A%20%20x%20%3D%3E%20x%20%3E%200%2C%0A%20%20%5B'a'%2C%20'b'%2C%20'c'%5D%2C%0A%20%20%7Ba%3A%20%7Bb%3A%20%7Bc%3A%201%7D%7D%7D%0A)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.pathSatisfies</strong> example in Rambda REPL</a>

pick

pick<T, K extends string | number | symbol>(propsToPick: K[], input: T): Pick<T, Exclude<keyof T, Exclude<keyof T, K>>>

It returns a partial copy of an input containing only propsToPick properties.

input can be either an object or an array.

String annotation of propsToPick is one of the differences between Rambda and Ramda.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7B%0A%20%20a%20%3A%201%2C%0A%20%20b%20%3A%20false%2C%0A%20%20foo%3A%20'cherry'%0A%7D%0Aconst%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20propsToPick%20%3D%20'a%2Cfoo'%0Aconst%20propsToPickList%20%3D%20%5B'a'%2C%20'foo'%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.pick(propsToPick%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pick(propsToPickList%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pick('a%2Cbar'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pick('bar'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pick(%5B0%2C%203%2C%205%5D%2C%20list)%2C%0A%20%20R.pick('0%2C3%2C5'%2C%20list)%2C%0A%5D%0A%0Aconst%20expected%20%3D%20%5B%0A%20%20%7Ba%3A1%2C%20foo%3A%20'cherry'%7D%2C%0A%20%20%7Ba%3A1%2C%20foo%3A%20'cherry'%7D%2C%0A%20%20%7Ba%3A1%7D%2C%0A%20%20%7B%7D%2C%0A%20%20%7B0%3A%201%2C%203%3A%204%7D%2C%0A%20%20%7B0%3A%201%2C%203%3A%204%7D%2C%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.pick</strong> example in Rambda REPL</a>

pick<T, K extends string | number | symbol>(propsToPick: K[], input: T): Pick<T, Exclude<keyof T, Exclude<keyof T, K>>>;
pick<K extends string | number | symbol>(propsToPick: K[]): <T>(input: T) => Pick<T, Exclude<keyof T, Exclude<keyof T, K>>>;
pick<T, U>(propsToPick: string, input: T): U;
pick<T, U>(propsToPick: string): (input: T) => U;
pick<T>(propsToPick: string, input: object): T;
pick<T>(propsToPick: string): (input: object) => T;

import { createPath } from './_internals/createPath.js'

export function pick(propsToPick, input){
  if (arguments.length === 1) return _input => pick(propsToPick, _input)

  if (input === null || input === undefined){
    return undefined
  }
  const keys = createPath(propsToPick, ',')
  const willReturn = {}
  let counter = 0

  while (counter < keys.length){
    if (keys[ counter ] in input){
      willReturn[ keys[ counter ] ] = input[ keys[ counter ] ]
    }
    counter++
  }

  return willReturn
}

import { pick } from './pick.js'

const obj = {
  a : 1,
  b : 2,
  c : 3,
}

test('props to pick is a string', () => {
  const result = pick('a,c', obj)
  const resultCurry = pick('a,c')(obj)
  const expectedResult = {
    a : 1,
    c : 3,
  }

  expect(result).toEqual(expectedResult)
  expect(resultCurry).toEqual(expectedResult)
})

test('when prop is missing', () => {
  const result = pick('a,d,f', obj)
  expect(result).toEqual({ a : 1 })
})

test('with list indexes as props', () => {
  const list = [ 1, 2, 3 ]
  const expected = {
    0 : 1,
    2 : 3,
  }
  expect(pick([ 0, 2, 3 ], list)).toEqual(expected)
  expect(pick('0,2,3', list)).toEqual(expected)
})

test('props to pick is an array', () => {
  expect(pick([ 'a', 'c' ])({
    a : 'foo',
    b : 'bar',
    c : 'baz',
  })).toEqual({
    a : 'foo',
    c : 'baz',
  })

  expect(pick([ 'a', 'd', 'e', 'f' ])({
    a : 'foo',
    b : 'bar',
    c : 'baz',
  })).toEqual({ a : 'foo' })

  expect(pick('a,d,e,f')(null)).toBeUndefined()
})

test('works with list as input and number as props - props to pick is an array', () => {
  const result = pick([ 1, 2 ], [ 'a', 'b', 'c', 'd' ])
  expect(result).toEqual({
    1 : 'b',
    2 : 'c',
  })
})

test('works with list as input and number as props - props to pick is a string', () => {
  const result = pick('1,2', [ 'a', 'b', 'c', 'd' ])
  expect(result).toEqual({
    1 : 'b',
    2 : 'c',
  })
})

test('with symbol', () => {
  const symbolProp = Symbol('s')
  expect(pick([ symbolProp ], { [ symbolProp ] : 'a' })).toMatchInlineSnapshot(`
{
  Symbol(s): "a",
}
`)
})

import {pick} from 'rambda'

const input = {a: 'foo', b: 2, c: 3, d: 4}

describe('R.pick with array as props input', () => {
  it('without passing type', () => {
    const result = pick(['a', 'c'], input)
    result.a // $ExpectType string
    result.c // $ExpectType number
  })
})

describe('R.pick with string as props input', () => {
  interface Input {
    a: string,
    b: number,
    c: number,
    d: number,
  }
  interface Output {
    a: string,
    c: number,
  }
  it('explicitly declare output', () => {
    const result = pick<Output>('a,c', input)
    result // $ExpectType Output
    result.a // $ExpectType string
    result.c // $ExpectType number

    const curriedResult = pick<Output>('a,c')(input)

    curriedResult.a // $ExpectType string
  })

  it('explicitly declare input and output', () => {
    const result = pick<Input, Output>('a,c', input)
    result // $ExpectType Output
    result.a // $ExpectType string

    const curriedResult = pick<Input, Output>('a,c')(input)

    curriedResult.a // $ExpectType string
  })

  it('without passing type', () => {
    const result = pick('a,c', input)
    result // $ExpectType unknown
  })
})

pickAll

pickAll<T, K extends keyof T>(propsToPicks: K[], input: T): Pick<T, K>

Same as R.pick but it won't skip the missing props, i.e. it will assign them to undefined.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7B%0A%20%20a%20%3A%201%2C%0A%20%20b%20%3A%20false%2C%0A%20%20foo%3A%20'cherry'%0A%7D%0Aconst%20propsToPick%20%3D%20'a%2Cfoo%2Cbar'%0Aconst%20propsToPickList%20%3D%20%5B'a'%2C%20'foo'%2C%20'bar'%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.pickAll(propsToPick%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pickAll(propsToPickList%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pickAll('a%2Cbar'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.pickAll('bar'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%5D%0Aconst%20expected%20%3D%20%5B%0A%20%20%7Ba%3A1%2C%20foo%3A%20'cherry'%2C%20bar%3A%20undefined%7D%2C%0A%20%20%7Ba%3A1%2C%20foo%3A%20'cherry'%2C%20bar%3A%20undefined%7D%2C%0A%20%20%7Ba%3A1%2C%20bar%3A%20undefined%7D%2C%0A%20%20%7Bbar%3A%20undefined%7D%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.pickAll</strong> example in Rambda REPL</a>

pickAll<T, K extends keyof T>(propsToPicks: K[], input: T): Pick<T, K>;
pickAll<T, U>(propsToPicks: string[], input: T): U;
pickAll(propsToPicks: string[]): <T, U>(input: T) => U;
pickAll<T, U>(propsToPick: string, input: T): U;
pickAll<T, U>(propsToPick: string): (input: T) => U;

import { createPath } from './_internals/createPath.js'

export function pickAll(propsToPick, obj){
  if (arguments.length === 1) return _obj => pickAll(propsToPick, _obj)

  if (obj === null || obj === undefined){
    return undefined
  }
  const keysValue = createPath(propsToPick, ',')
  const willReturn = {}
  let counter = 0

  while (counter < keysValue.length){
    if (keysValue[ counter ] in obj){
      willReturn[ keysValue[ counter ] ] = obj[ keysValue[ counter ] ]
    } else {
      willReturn[ keysValue[ counter ] ] = undefined
    }
    counter++
  }

  return willReturn
}

import { pickAll } from './pickAll.js'

test('when input is undefined or null', () => {
  expect(pickAll('a', null)).toBeUndefined()
  expect(pickAll('a', undefined)).toBeUndefined()
})

test('with string as condition', () => {
  const obj = {
    a : 1,
    b : 2,
    c : 3,
  }
  const result = pickAll('a,c', obj)
  const resultCurry = pickAll('a,c')(obj)
  const expectedResult = {
    a : 1,
    b : undefined,
    c : 3,
  }

  expect(result).toEqual(expectedResult)
  expect(resultCurry).toEqual(expectedResult)
})

test('with array as condition', () => {
  expect(pickAll([ 'a', 'b', 'c' ], {
    a : 'foo',
    c : 'baz',
  })).toEqual({
    a : 'foo',
    b : undefined,
    c : 'baz',
  })
})

import {pickAll} from 'rambda'

interface Input {
  a: string,
  b: number,
  c: number,
  d: number,
}
interface Output {
  a?: string,
  c?: number,
}
const input = {a: 'foo', b: 2, c: 3, d: 4}

describe('R.pickAll with array as props input', () => {
  it('without passing type', () => {
    const result = pickAll(['a', 'c'], input)
    result.a // $ExpectType string
    result.c // $ExpectType number
  })
  it('without passing type + curry', () => {
    const result = pickAll(['a', 'c'])(input)
    result // $ExpectType unknown
  })
  it('explicitly passing types', () => {
    const result = pickAll<Input, Output>(['a', 'c'], input)
    result.a // $ExpectType string | undefined
    result.c // $ExpectType number | undefined
  })
})

describe('R.pickAll with string as props input', () => {
  it('without passing type', () => {
    const result = pickAll('a,c', input)
    result // $ExpectType unknown
  })
  it('without passing type + curry', () => {
    const result = pickAll('a,c')(input)
    result // $ExpectType unknown
  })
  it('explicitly passing types', () => {
    const result = pickAll<Input, Output>('a,c', input)
    result.a // $ExpectType string | undefined
    result.c // $ExpectType number | undefined
  })
  it('explicitly passing types + curry', () => {
    const result = pickAll<Input, Output>('a,c')(input)
    result.a // $ExpectType string | undefined
    result.c // $ExpectType number | undefined
  })
})

pickBy

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.pickBy(%0A%20%20x%20%3D%3E%20x%20%3E%201%2C%0A%20%20%7Ba%3A%201%2C%20b%3A%202%2C%20c%3A%203%7D%0A)%0A%2F%2F%20%3D%3E%20%7Bb%3A%202%2C%20c%3A%203%7D">Try this <strong>R.pickBy</strong> example in Rambda REPL</a>

pipe

It performs left-to-right function composition.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.pipe(%0A%20%20R.filter(val%20%3D%3E%20val%20%3E%202)%2C%0A%20%20R.map(a%20%3D%3E%20a%20*%202)%0A)(%5B1%2C%202%2C%203%2C%204%5D)%0A%0A%2F%2F%20%3D%3E%20%5B6%2C%208%5D">Try this <strong>R.pipe</strong> example in Rambda REPL</a>

pluck

pluck<K extends keyof T, T>(property: K, list: T[]): T[K][]

It returns list of the values of property taken from the all objects inside list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%7Ba%3A%201%7D%2C%20%7Ba%3A%202%7D%2C%20%7Bb%3A%203%7D%5D%0Aconst%20property%20%3D%20'a'%0A%0Aconst%20result%20%3D%20R.pluck(property%2C%20list)%20%0A%2F%2F%20%3D%3E%20%5B1%2C%202%5D">Try this <strong>R.pluck</strong> example in Rambda REPL</a>

pluck<K extends keyof T, T>(property: K, list: T[]): T[K][];
pluck<T>(property: number, list: { [k: number]: T }[]):  T[];
pluck<P extends string>(property: P): <T>(list: Record<P, T>[]) => T[];
pluck(property: number): <T>(list: { [k: number]: T }[]) => T[];

import { map } from './map.js'

export function pluck(property, list){
  if (arguments.length === 1) return _list => pluck(property, _list)

  const willReturn = []

  map(x => {
    if (x[ property ] !== undefined){
      willReturn.push(x[ property ])
    }
  }, list)

  return willReturn
}

import { pluck } from './pluck.js'

test('happy', () => {
  expect(pluck('a')([ { a : 1 }, { a : 2 }, { b : 1 } ])).toEqual([ 1, 2 ])
})

test('with undefined', () => {
  expect(pluck(undefined)([ { a : 1 }, { a : 2 }, { b : 1 } ])).toEqual([ ])
})

test('with number', () => {
  const input = [
    [ 1, 2 ],
    [ 3, 4 ],
  ]

  expect(pluck(0, input)).toEqual([ 1, 3 ])
})

import {pluck} from 'rambda'

describe('R.pluck', () => {
  it('with object', () => {
    interface ListMember {
      a: number,
      b: string,
    }
    const input: ListMember[] = [
      {a: 1, b: 'foo'},
      {a: 2, b: 'bar'},
    ]
    const resultA = pluck('a', input)
    const resultB = pluck('b')(input)
    resultA // $ExpectType number[]
    resultB // $ExpectType string[]
  })

  it('with array', () => {
    const input = [
      [1, 2],
      [3, 4],
      [5, 6],
    ]
    const result = pluck(0, input)
    const resultCurry = pluck(0)(input)
    result // $ExpectType number[]
    resultCurry // $ExpectType number[]
  })
})

prepend

prepend<T>(xToPrepend: T, iterable: T[]): T[]

It adds element x at the beginning of list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.prepend('foo'%2C%20%5B'bar'%2C%20'baz'%5D)%0A%2F%2F%20%3D%3E%20%5B'foo'%2C%20'bar'%2C%20'baz'%5D">Try this <strong>R.prepend</strong> example in Rambda REPL</a>

prepend<T>(xToPrepend: T, iterable: T[]): T[];
prepend<T, U>(xToPrepend: T, iterable: IsFirstSubtypeOfSecond<T, U>[]) : U[];
prepend<T>(xToPrepend: T): <U>(iterable: IsFirstSubtypeOfSecond<T, U>[]) => U[];
prepend<T>(xToPrepend: T): (iterable: T[]) => T[];

export function prepend(x, input){
  if (arguments.length === 1) return _input => prepend(x, _input)

  if (typeof input === 'string') return [ x ].concat(input.split(''))

  return [ x ].concat(input)
}

import { prepend } from './prepend.js'

test('happy', () => {
  expect(prepend('yes', [ 'foo', 'bar', 'baz' ])).toEqual([
    'yes',
    'foo',
    'bar',
    'baz',
  ])
})

test('with empty list', () => {
  expect(prepend('foo')([])).toEqual([ 'foo' ])
})

test('with string instead of array', () => {
  expect(prepend('foo')('bar')).toEqual([ 'foo', 'b', 'a', 'r' ])
})

product

product(list: number[]): number

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.product(%5B%202%2C%203%2C%204%20%5D)%0A%2F%2F%20%3D%3E%2024)">Try this <strong>R.product</strong> example in Rambda REPL</a>

product(list: number[]): number;

import { multiply } from './multiply.js'
import { reduce } from './reduce.js'

export const product = reduce(multiply, 1)

import { product } from './product.js'

test('happy', () => {
  expect(product([ 2, 3, 4 ])).toBe(24)
})

test('bad input', () => {
  expect(product([ null ])).toBe(0)
  expect(product([])).toBe(1)
})

import {product} from 'rambda'

describe('R.product', () => {
  it('happy', () => {
    const result = product([1, 2, 3])

    result // $ExpectType number
  })
})

prop

prop<_, P extends keyof never, T>(p: P, value: T): Prop<T, P>

It returns the value of property propToFind in obj.

If there is no such property, it returns undefined.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.prop('x'%2C%20%7Bx%3A%20100%7D)%2C%20%0A%20%20R.prop('x'%2C%20%7Ba%3A%201%7D)%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B100%2C%20undefined%5D">Try this <strong>R.prop</strong> example in Rambda REPL</a>

prop<_, P extends keyof never, T>(p: P, value: T): Prop<T, P>;
prop<V>(p: keyof never, value: unknown): V;
prop<_, P extends keyof never>(p: P): <T>(value: T) => Prop<T, P>;
prop<V>(p: keyof never): (value: unknown) => V;

export function propFn(searchProperty, obj){
  if (!obj) return undefined

  return obj[ searchProperty ]
}

export function prop(searchProperty, obj){
  if (arguments.length === 1) return _obj => prop(searchProperty, _obj)

  return propFn(searchProperty, obj)
}

import { prop } from './prop.js'

test('prop', () => {
  expect(prop('foo')({ foo : 'baz' })).toBe('baz')

  expect(prop('bar')({ foo : 'baz' })).toBeUndefined()

  expect(prop('bar')(null)).toBeUndefined()
})

import {prop} from 'rambda'

describe('R.prop', () => {
  interface Foo {
    a: number,
    b: string,
    c?: number,
  }
  const obj: Foo = {a: 1, b: 'foo'}

  it('issue #553', () => {
    const result = {
      a: prop('a', obj),
      b: prop('b', obj),
      c: prop('c', obj),
    }
    const curriedResult = {
      a: prop('a')(obj),
      b: prop('b')(obj),
      c: prop('c')(obj),
    }

    result // $ExpectType { a: number; b: string; c: number | undefined; }
    curriedResult // $ExpectType { a: number; b: string; c: number | undefined; }
  })
})

describe('with number as prop', () => {
  const list = [1, 2, 3]
  const index = 1
  it('happy', () => {
    const result = prop(index, list)

    result // $ExpectType number
  })
  it('curried require explicit type', () => {
    const result = prop<number>(index)(list)

    result // $ExpectType number
  })
})

propEq

propEq<K extends string | number>(valueToMatch: any, propToFind: K, obj: Record<K, any>): boolean

It returns true if obj has property propToFind and its value is equal to valueToMatch.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7B%20foo%3A%20'bar'%20%7D%0Aconst%20secondObj%20%3D%20%7B%20foo%3A%201%20%7D%0A%0Aconst%20propToFind%20%3D%20'foo'%0Aconst%20valueToMatch%20%3D%20'bar'%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.propEq(propToFind%2C%20valueToMatch%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.propEq(propToFind%2C%20valueToMatch%2C%20secondRecord%3Cstring%2C%20unknown%3E)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.propEq</strong> example in Rambda REPL</a>

propEq<K extends string | number>(valueToMatch: any, propToFind: K, obj: Record<K, any>): boolean;
propEq<K extends string | number>(valueToMatch: any, propToFind: K): (obj: Record<K, any>) => boolean;
propEq(valueToMatch: any): {
  <K extends string | number>(propToFind: K, obj: Record<K, any>): boolean;
  <K extends string | number>(propToFind: K): (obj: Record<K, any>) => boolean;
};

import { curry } from './curry.js'
import { equals } from './equals.js'
import { prop } from './prop.js'

function propEqFn(
  valueToMatch, propToFind, obj
){
  if (!obj) return false

  return equals(valueToMatch, prop(propToFind, obj))
}

export const propEq = curry(propEqFn)

import { BAR, FOO } from './_internals/testUtils.js'
import { propEq } from './propEq.js'

test('happy', () => {
  const obj = { [ FOO ] : BAR }
  expect(propEq(BAR, FOO)(obj)).toBeTrue()
  expect(propEq(1, FOO)(obj)).toBeFalse()
  expect(propEq(1)(FOO)(obj)).toBeFalse()
  expect(propEq(
    1, 1, null
  )).toBeFalse()
})

test('returns false if called with a null or undefined object', () => {
  expect(propEq(
    'name', 'Abby', null
  )).toBeFalse()
  expect(propEq(
    'name', 'Abby', undefined
  )).toBeFalse()
})

import {propEq} from 'rambda'

const property = 'foo'
const numberProperty = 1
const value = 'bar'
const obj = {[property]: value}
const objWithNumberIndex = {[numberProperty]: value}

describe('R.propEq', () => {
  it('happy', () => {
    const result = propEq(value, property, obj)
    result // $ExpectType boolean
  })

  it('number is property', () => {
    const result = propEq(value, 1, objWithNumberIndex)
    result // $ExpectType boolean
  })

  it('with optional property', () => {
    interface MyType {
      optional?: string | number,
    }

    const myObject: MyType = {}
    const valueToFind = '1111'
    // @ts-expect-error
    propEq(valueToFind, 'optional', myObject)
  })

  it('imported from @types/ramda', () => {
    interface A {
      foo: string | null,
    }
    const obj: A = {
      foo: 'bar',
    }
    const value = ''
    const result = propEq(value, 'foo')(obj)
    result // $ExpectType boolean

    // @ts-expect-error
    propEq(value, 'bar')(obj)
  })
})

propIs

propIs<C extends AnyFunction, K extends keyof any>(type: C, name: K, obj: any): obj is Record<K, ReturnType<C>>

It returns true if property of obj is from target type.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A1%2C%20b%3A%20'foo'%7D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.propIs(Number%2C%20'a'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.propIs(String%2C%20'b'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.propIs(Number%2C%20'b'%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%2C%20false%5D">Try this <strong>R.propIs</strong> example in Rambda REPL</a>

propIs<C extends AnyFunction, K extends keyof any>(type: C, name: K, obj: any): obj is Record<K, ReturnType<C>>;
propIs<C extends AnyConstructor, K extends keyof any>(type: C, name: K, obj: any): obj is Record<K, InstanceType<C>>;
propIs<C extends AnyFunction, K extends keyof any>(type: C, name: K): (obj: any) => obj is Record<K, ReturnType<C>>;
propIs<C extends AnyConstructor, K extends keyof any>(type: C, name: K): (obj: any) => obj is Record<K, InstanceType<C>>;
propIs<C extends AnyFunction>(type: C): {
    <K extends keyof any>(name: K, obj: any): obj is Record<K, ReturnType<C>>;
    <K extends keyof any>(name: K): (obj: any) => obj is Record<K, ReturnType<C>>;
};

import { curry } from './curry.js'
import { is } from './is.js'

function propIsFn(
  targetPrototype, property, obj
){
  return is(targetPrototype, obj[ property ])
}

export const propIs = curry(propIsFn)

import { propIs } from './propIs.js'

const obj = {
  a : 1,
  b : 'foo',
}

test('when true', () => {
  expect(propIs(
    Number, 'a', obj
  )).toBeTrue()
  expect(propIs(
    String, 'b', obj
  )).toBeTrue()
})

test('when false', () => {
  expect(propIs(
    String, 'a', obj
  )).toBeFalse()
  expect(propIs(
    Number, 'b', obj
  )).toBeFalse()
})

import {propIs} from 'rambda'

const property = 'a'
const obj = {a: 1}

describe('R.propIs', () => {
  it('happy', () => {
    const result = propIs(Number, property, obj)
    result // $ExpectType boolean
  })

  it('curried', () => {
    const result = propIs(Number, property)(obj)
    result // $ExpectType boolean
  })
})

propOr

propOr<T, P extends string>(defaultValue: T, property: P, obj: Partial<Record<P, T>> | undefined): T

It returns either defaultValue or the value of property in obj.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A%201%7D%0Aconst%20defaultValue%20%3D%20'DEFAULT_VALUE'%0Aconst%20property%20%3D%20'a'%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.propOr(defaultValue%2C%20property%2C%20Record%3Cstring%2C%20unknown%3E)%2C%0A%20%20R.propOr(defaultValue%2C%20'foo'%2C%20Record%3Cstring%2C%20unknown%3E)%0A%5D%0A%2F%2F%20%3D%3E%20%5B1%2C%20'DEFAULT_VALUE'%5D">Try this <strong>R.propOr</strong> example in Rambda REPL</a>

propOr<T, P extends string>(defaultValue: T, property: P, obj: Partial<Record<P, T>> | undefined): T;
propOr<T, P extends string>(defaultValue: T, property: P): (obj: Partial<Record<P, T>> | undefined) => T;
propOr<T>(defaultValue: T): {
  <P extends string>(property: P, obj: Partial<Record<P, T>> | undefined): T;
  <P extends string>(property: P): (obj: Partial<Record<P, T>> | undefined) => T;
}

import { curry } from './curry.js'
import { defaultTo } from './defaultTo.js'

function propOrFn(
  defaultValue, property, obj
){
  if (!obj) return defaultValue

  return defaultTo(defaultValue, obj[ property ])
}

export const propOr = curry(propOrFn)

import { propOr } from './propOr.js'

test('propOr (result)', () => {
  const obj = { a : 1 }
  expect(propOr(
    'default', 'a', obj
  )).toBe(1)
  expect(propOr(
    'default', 'notExist', obj
  )).toBe('default')
  expect(propOr(
    'default', 'notExist', null
  )).toBe('default')
})

test('propOr (currying)', () => {
  const obj = { a : 1 }
  expect(propOr('default')('a', obj)).toBe(1)
  expect(propOr('default', 'a')(obj)).toBe(1)
  expect(propOr('default')('notExist', obj)).toBe('default')
  expect(propOr('default', 'notExist')(obj)).toBe('default')
})

import {propOr} from 'rambda'

const obj = {foo: 'bar'}
const property = 'foo'
const fallback = 'fallback'

describe('R.propOr', () => {
  it('happy', () => {
    const result = propOr(fallback, property, obj)
    result // $ExpectType string
  })
  it('curry 1', () => {
    const result = propOr(fallback)(property, obj)
    result // $ExpectType string
  })
  it('curry 2', () => {
    const result = propOr(fallback, property)(obj)
    result // $ExpectType string
  })
  it('curry 3', () => {
    const result = propOr(fallback)(property)(obj)
    result // $ExpectType string
  })
})

props

props<P extends string, T>(propsToPick: P[], obj: Record<P, T>): T[]

It takes list with properties propsToPick and returns a list with property values in obj.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.props(%0A%20%20%5B'a'%2C%20'b'%5D%2C%20%0A%20%20%7Ba%3A1%2C%20c%3A3%7D%0A)%0A%2F%2F%20%3D%3E%20%5B1%2C%20undefined%5D">Try this <strong>R.props</strong> example in Rambda REPL</a>

props<P extends string, T>(propsToPick: P[], obj: Record<P, T>): T[];
props<P extends string>(propsToPick: P[]): <T>(obj: Record<P, T>) => T[];
props<P extends string, T>(propsToPick: P[]): (obj: Record<P, T>) => T[];

import { isArray } from './_internals/isArray.js'
import { mapArray } from './map.js'

export function props(propsToPick, obj){
  if (arguments.length === 1){
    return _obj => props(propsToPick, _obj)
  }
  if (!isArray(propsToPick)){
    throw new Error('propsToPick is not a list')
  }

  return mapArray(prop => obj[ prop ], propsToPick)
}

import { props } from './props.js'

const obj = {
  a : 1,
  b : 2,
}
const propsToPick = [ 'a', 'c' ]

test('happy', () => {
  const result = props(propsToPick, obj)
  expect(result).toEqual([ 1, undefined ])
})

test('curried', () => {
  const result = props(propsToPick)(obj)
  expect(result).toEqual([ 1, undefined ])
})

test('wrong input', () => {
  expect(() => props(null)(obj)).toThrowErrorMatchingInlineSnapshot('"propsToPick is not a list"')
})

import {props} from 'rambda'

const obj = {a: 1, b: 2}

describe('R.props', () => {
  it('happy', () => {
    const result = props(['a', 'b'], obj)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = props(['a', 'b'])(obj)

    result // $ExpectType number[]
  })
})

propSatisfies

propSatisfies<T>(predicate: Predicate<T>, property: string, obj: Record<string, T>): boolean

It returns true if the object property satisfies a given predicate.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A%20%7Bb%3A1%7D%7D%0Aconst%20property%20%3D%20'a'%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%3F.b%20%3D%3D%3D%201%0A%0Aconst%20result%20%3D%20R.propSatisfies(predicate%2C%20property%2C%20Record%3Cstring%2C%20unknown%3E)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.propSatisfies</strong> example in Rambda REPL</a>

propSatisfies<T>(predicate: Predicate<T>, property: string, obj: Record<string, T>): boolean;
propSatisfies<T>(predicate: Predicate<T>, property: string): (obj: Record<string, T>) => boolean;

import { curry } from './curry.js'
import { prop } from './prop.js'

function propSatisfiesFn(
  predicate, property, obj
){
  return predicate(prop(property, obj))
}

export const propSatisfies = curry(propSatisfiesFn)

import { propSatisfies } from './propSatisfies.js'

const obj = { a : 1 }

test('when true', () => {
  expect(propSatisfies(
    x => x > 0, 'a', obj
  )).toBeTrue()
})

test('when false', () => {
  expect(propSatisfies(x => x < 0, 'a')(obj)).toBeFalse()
})

import {propSatisfies} from 'rambda'

const obj = {a: 1}

describe('R.propSatisfies', () => {
  it('happy', () => {
    const result = propSatisfies(x => x > 0, 'a', obj)

    result // $ExpectType boolean
  })
  it('curried requires explicit type', () => {
    const result = propSatisfies<number>(x => x > 0, 'a')(obj)

    result // $ExpectType boolean
  })
})

range

range(startInclusive: number, endExclusive: number): number[]

It returns list of numbers between startInclusive to endExclusive markers.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.range(0%2C%205)%0A%2F%2F%20%3D%3E%20%5B0%2C%201%2C%202%2C%203%2C%204%5D">Try this <strong>R.range</strong> example in Rambda REPL</a>

range(startInclusive: number, endExclusive: number): number[];
range(startInclusive: number): (endExclusive: number) => number[];

export function range(start, end){
  if (arguments.length === 1) return _end => range(start, _end)

  if (Number.isNaN(Number(start)) || Number.isNaN(Number(end))){
    throw new TypeError('Both arguments to range must be numbers')
  }

  if (end < start) return []

  const len = end - start
  const willReturn = Array(len)

  for (let i = 0; i < len; i++){
    willReturn[ i ] = start + i
  }

  return willReturn
}

import { range } from './range.js'

test('happy', () => {
  expect(range(0, 10)).toEqual([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ])
})

test('end range is bigger than start range', () => {
  expect(range(7, 3)).toEqual([])
  expect(range(5, 5)).toEqual([])
})

test('with bad input', () => {
  const throwMessage = 'Both arguments to range must be numbers'
  expect(() => range('a', 6)).toThrowWithMessage(Error, throwMessage)
  expect(() => range(6, 'z')).toThrowWithMessage(Error, throwMessage)
})

test('curry', () => {
  expect(range(0)(10)).toEqual([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ])
})

import {range} from 'rambda'

describe('R.range', () => {
  it('happy', () => {
    const result = range(1, 4)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = range(1)(4)

    result // $ExpectType number[]
  })
})

reduce

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%5D%0Aconst%20initialValue%20%3D%2010%0Aconst%20reducer%20%3D%20(prev%2C%20current)%20%3D%3E%20prev%20*%20current%0A%0Aconst%20result%20%3D%20R.reduce(reducer%2C%20initialValue%2C%20list)%0A%2F%2F%20%3D%3E%2060">Try this <strong>R.reduce</strong> example in Rambda REPL</a>

reduceBy

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.reduceBy(%0A%20%20(acc%2C%20elem)%20%3D%3E%20acc%20%2B%20elem%2C%0A%20%200%2C%0A%20%20x%20%3D%3E%20x%20%3E%202%20%3F%20'big'%20%3A%20'small'%2C%0A%20%20%5B1%2C%202%2C%203%2C%204%2C%205%5D%0A)%0A%2F%2F%20%3D%3E%20%7B%20big%3A%2012%2C%20small%3A%203%20%7D">Try this <strong>R.reduceBy</strong> example in Rambda REPL</a>

reject

reject<T>(predicate: Predicate<T>, list: T[]): T[]

It has the opposite effect of R.filter.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20obj%20%3D%20%7Ba%3A%201%2C%20b%3A%202%7D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3E%201%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.reject(predicate%2C%20list)%2C%0A%20%20R.reject(predicate%2C%20Record%3Cstring%2C%20unknown%3E)%0A%5D%0A%2F%2F%20%3D%3E%20%5B%5B1%5D%2C%20%7Ba%3A%201%7D%5D">Try this <strong>R.reject</strong> example in Rambda REPL</a>

reject<T>(predicate: Predicate<T>, list: T[]): T[];
reject<T>(predicate: Predicate<T>): (list: T[]) => T[];
reject<T>(predicate: Predicate<T>, obj: Dictionary<T>): Dictionary<T>;
reject<T, U>(predicate: Predicate<T>): (obj: Dictionary<T>) => Dictionary<T>;

import { filter } from './filter.js'

export function reject(predicate, list){
  if (arguments.length === 1) return _list => reject(predicate, _list)

  return filter(x => !predicate(x), list)
}

import { reject } from './reject.js'

const isOdd = n => n % 2 === 1

test('with array', () => {
  expect(reject(isOdd)([ 1, 2, 3, 4 ])).toEqual([ 2, 4 ])
})

test('with object', () => {
  const obj = {
    a : 1,
    b : 2,
    c : 3,
    d : 4,
  }
  expect(reject(isOdd, obj)).toEqual({
    b : 2,
    d : 4,
  })
})

import {reject} from 'rambda'

describe('R.reject with array', () => {
  it('happy', () => {
    const result = reject(
      x => {
        x // $ExpectType number
        return x > 1
      },
      [1, 2, 3]
    )
    result // $ExpectType number[]
  })
  it('curried require explicit type', () => {
    const result = reject<number>(x => {
      x // $ExpectType number
      return x > 1
    })([1, 2, 3])
    result // $ExpectType number[]
  })
})

describe('R.reject with objects', () => {
  it('happy', () => {
    const result = reject(
      x => {
        x // $ExpectType number

        return x > 1
      },
      {a: 1, b: 2}
    )
    result // $ExpectType Dictionary<number>
  })
  it('curried require dummy type', () => {
    const result = reject<number, any>(x => {
      return x > 1
    })({a: 1, b: 2})
    result // $ExpectType Dictionary<number>
  })
})

removeIndex

removeIndex<T>(index: number, list: T[]): T[]

It returns a copy of list input with removed index.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20result%20%3D%20R.removeIndex(1%2C%20list)%0A%2F%2F%20%3D%3E%20%5B1%2C%203%2C%204%5D">Try this <strong>R.removeIndex</strong> example in Rambda REPL</a>

removeIndex<T>(index: number, list: T[]): T[];
removeIndex(index: number): <T>(list: T[]) => T[];

export function removeIndex(index, list){
  if (arguments.length === 1) return _list => removeIndex(index, _list)
  if (index <= 0) return list.slice(1)
  if (index >= list.length - 1) return list.slice(0, list.length - 1)

  return [ ...list.slice(0, index), ...list.slice(index + 1) ]
}

import { removeIndex } from './removeIndex.js'

const list = [ 1, 2, 3, 4 ]

test('first or before first index', () => {
  expect(removeIndex(-2, list)).toEqual([ 2, 3, 4 ])
  expect(removeIndex(-2)(list)).toEqual([ 2, 3, 4 ])
})

test('last or after last index', () => {
  expect(removeIndex(4, list)).toEqual([ 1, 2, 3 ])
  expect(removeIndex(10, list)).toEqual([ 1, 2, 3 ])
})

test('middle index', () => {
  expect(removeIndex(1, list)).toEqual([ 1, 3, 4 ])
  expect(removeIndex(2, list)).toEqual([ 1, 2, 4 ])
})

import {removeIndex} from 'rambda'

describe('R.removeIndex', () => {
  it('happy', () => {
    const result = removeIndex(1, [1, 2, 3])

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = removeIndex(1)([1, 2, 3])

    result // $ExpectType number[]
  })
})

repeat

repeat<T>(x: T): (timesToRepeat: number) => T[]

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.repeat('foo'%2C%203)%0A%2F%2F%20%3D%3E%20%5B'foo'%2C%20'foo'%2C%20'foo'%5D">Try this <strong>R.repeat</strong> example in Rambda REPL</a>

repeat<T>(x: T): (timesToRepeat: number) => T[];
repeat<T>(x: T, timesToRepeat: number): T[];

export function repeat(x, timesToRepeat){
  if (arguments.length === 1){
    return _timesToRepeat => repeat(x, _timesToRepeat)
  }

  return Array(timesToRepeat).fill(x)
}

import { repeat } from './repeat.js'

test('repeat', () => {
  expect(repeat('')(3)).toEqual([ '', '', '' ])
  expect(repeat('foo', 3)).toEqual([ 'foo', 'foo', 'foo' ])

  const obj = {}
  const arr = repeat(obj, 3)

  expect(arr).toEqual([ {}, {}, {} ])

  expect(arr[ 0 ] === arr[ 1 ]).toBeTrue()
})

import {repeat} from 'rambda'

describe('R.repeat', () => {
  it('happy', () => {
    const result = repeat(4, 7)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = repeat(4)(7)

    result // $ExpectType number[]
  })
})

replace

replace(strOrRegex: RegExp | string, replacer: RegExpReplacer, str: string): string

It replaces strOrRegex found in str with replacer.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20strOrRegex%20%3D%20%2Fo%2Fg%0A%0Aconst%20result%20%3D%20R.replace(strOrRegex%2C%20'%7C0%7C'%2C%20'foo')%0A%2F%2F%20%3D%3E%20'f%7C0%7C%7C0%7C'">Try this <strong>R.replace</strong> example in Rambda REPL</a>

replace(strOrRegex: RegExp | string, replacer: RegExpReplacer, str: string): string;
replace(strOrRegex: RegExp | string, replacer: RegExpReplacer): (str: string) => string;
replace(strOrRegex: RegExp | string): (replacer: RegExpReplacer) => (str: string) => string;

import { curry } from './curry.js'

function replaceFn(
  pattern, replacer, str
){
  return str.replace(pattern, replacer)
}

export const replace = curry(replaceFn)

import { replace } from './replace.js'

test('happy', () => {
  expect(replace(
    /\s/g, '|', 'foo bar baz'
  )).toBe('foo|bar|baz')
})

test('with function as replacer input', () => {
  expect(replace(
    /\s/g,
    (
      match, offset, str
    ) => {
      expect(match).toBe(' ')
      expect([ 3, 7 ].includes(offset)).toBeTrue()
      expect(str).toBe('foo bar baz')

      return '|'
    },
    'foo bar baz'
  )).toBe('foo|bar|baz')
})

import {replace} from 'rambda'

const str = 'foo bar foo'
const replacer = 'bar'

describe('R.replace', () => {
  it('happy', () => {
    const result = replace(/foo/g, replacer, str)

    result // $ExpectType string
  })
  it('with string as search pattern', () => {
    const result = replace('foo', replacer, str)

    result // $ExpectType string
  })
  it('with function as replacer', () => {
    const result = replace('f(o)o', (m: string, p1: string, offset: number) => {
      m // $ExpectType string
      p1 // $ExpectType string
      offset // $ExpectType number
      return p1
    }, str)

    result // $ExpectType string
  })
})

describe('R.replace - curried', () => {
  it('happy', () => {
    const result = replace(/foo/g, replacer)(str)

    result // $ExpectType string
  })
  it('with string as search pattern', () => {
    const result = replace('foo', replacer)(str)

    result // $ExpectType string
  })
  it('with function as replacer', () => {
    const result = replace('f(o)o')((m: string, p1: string, offset: number) => {
      m // $ExpectType string
      p1 // $ExpectType string
      offset // $ExpectType number
      return p1
    })(str)

    result // $ExpectType string
  })
})

reverse

reverse<T>(input: T[]): T[]

It returns a reversed copy of list or string input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.reverse('foo')%2C%0A%20%20R.reverse(%5B1%2C%202%2C%203%5D)%0A%5D%0A%2F%2F%20%3D%3E%20%5B'oof'%2C%20%5B3%2C%202%2C%201%5D">Try this <strong>R.reverse</strong> example in Rambda REPL</a>

reverse<T>(input: T[]): T[];
reverse(input: string): string;

export function reverse(listOrString) {
  if (typeof listOrString === 'string') {
    return listOrString.split('').reverse().join('')
  }

  const clone = listOrString.slice()

  return clone.reverse()
}

import {reverse} from './reverse.js'

test('happy', () => {
  expect(reverse([1, 2, 3])).toEqual([3, 2, 1])
})

test('with string', () => {
  expect(reverse('baz')).toBe('zab')
})

test("it doesn't mutate", () => {
  const arr = [1, 2, 3]

  expect(reverse(arr)).toEqual([3, 2, 1])

  expect(arr).toEqual([1, 2, 3])
})

import {reverse} from 'rambda'

const list = [1, 2, 3, 4, 5]

describe('R.reverse', () => {
  it('happy', () => {
    const result = reverse(list)
    result // $ExpectType number[]
  })
})

set

set<S, A>(lens: Lens<S, A>): {
  (a: A): (obj: S) => S
  (a: A, obj: S): S
}

It returns a copied Object or Array with modified lens focus set to replacer value.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20input%20%3D%20%7Bx%3A%201%2C%20y%3A%202%7D%0Aconst%20xLens%20%3D%20R.lensProp('x')%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.set(xLens%2C%204%2C%20input)%2C%0A%20%20R.set(xLens%2C%208%2C%20input)%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B%7Bx%3A%204%2C%20y%3A%202%7D%2C%20%7Bx%3A%208%2C%20y%3A%202%7D%5D">Try this <strong>R.set</strong> example in Rambda REPL</a>

set<S, A>(lens: Lens<S, A>): {
  (a: A): (obj: S) => S
  (a: A, obj: S): S
};
set<S, A>(lens: Lens<S, A>, a: A): (obj: S) => S;
set<S, A>(lens: Lens<S, A>, a: A, obj: S): S;

import {always} from './always.js'
import {curry} from './curry.js'
import {over} from './over.js'

function setFn(lens, replacer, x) {
  return over(lens, always(replacer), x)
}

export const set = curry(setFn)

import {assoc} from './assoc.js'
import {lens} from './lens.js'
import {lensIndex} from './lensIndex.js'
import {lensPath} from './lensPath.js'
import {prop} from './prop.js'
import {set} from './set.js'

const testObject = {
  foo: 'bar',
  baz: {
    a: 'x',
    b: 'y',
  },
}

test('assoc lens', () => {
  const assocLens = lens(prop('foo'), assoc('foo'))
  const result = set(assocLens, 'FOO', testObject)
  const expected = {
    ...testObject,
    foo: 'FOO',
  }
  expect(result).toEqual(expected)
})

test('path lens', () => {
  const pathLens = lensPath('baz.a')
  const result = set(pathLens, 'z', testObject)
  const expected = {
    ...testObject,
    baz: {
      a: 'z',
      b: 'y',
    },
  }
  expect(result).toEqual(expected)
})

test('index lens', () => {
  const indexLens = lensIndex(0)

  const result = set(indexLens, 3, [1, 2])
  expect(result).toEqual([3, 2])
})

slice

slice(from: number, to: number, input: string): string

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B0%2C%201%2C%202%2C%203%2C%204%2C%205%5D%0Aconst%20str%20%3D%20'FOO_BAR'%0Aconst%20from%20%3D%201%0Aconst%20to%20%3D%204%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.slice(from%2C%20to%2C%20str)%2C%0A%20%20R.slice(from%2C%20to%2C%20list)%0A%5D%0A%2F%2F%20%3D%3E%20%5B'OO_'%2C%20%5B1%2C%202%2C%203%5D%5D">Try this <strong>R.slice</strong> example in Rambda REPL</a>

slice(from: number, to: number, input: string): string;
slice<T>(from: number, to: number, input: T[]): T[];
slice(from: number, to: number): {
  (input: string): string;
  <T>(input: T[]): T[];
};
slice(from: number): {
  (to: number, input: string): string;
  <T>(to: number, input: T[]): T[];
};

import { curry } from './curry.js'

function sliceFn(
  from, to, list
){
  return list.slice(from, to)
}

export const slice = curry(sliceFn)

import { slice } from './slice.js'

test('slice', () => {
  expect(slice(
    1, 3, [ 'a', 'b', 'c', 'd' ]
  )).toEqual([ 'b', 'c' ])
  expect(slice(
    1, Infinity, [ 'a', 'b', 'c', 'd' ]
  )).toEqual([ 'b', 'c', 'd' ])
  expect(slice(
    0, -1, [ 'a', 'b', 'c', 'd' ]
  )).toEqual([ 'a', 'b', 'c' ])
  expect(slice(
    -3, -1, [ 'a', 'b', 'c', 'd' ]
  )).toEqual([ 'b', 'c' ])
  expect(slice(
    0, 3, 'ramda'
  )).toBe('ram')
})

import {slice} from 'rambda'

const list = [1, 2, 3, 4, 5]

describe('R.slice', () => {
  it('happy', () => {
    const result = slice(1, 3, list)
    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = slice(1, 3)(list)
    result // $ExpectType number[]
  })
})

sort

sort<T>(sortFn: (a: T, b: T) => number, list: T[]): T[]

It returns copy of list sorted by sortFn function, where sortFn needs to return only -1, 0 or 1.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%0A%20%20%7Ba%3A%202%7D%2C%0A%20%20%7Ba%3A%203%7D%2C%0A%20%20%7Ba%3A%201%7D%0A%5D%0Aconst%20sortFn%20%3D%20(x%2C%20y)%20%3D%3E%20%7B%0A%20%20return%20x.a%20%3E%20y.a%20%3F%201%20%3A%20-1%0A%7D%0A%0Aconst%20result%20%3D%20R.sort(sortFn%2C%20list)%0Aconst%20expected%20%3D%20%5B%0A%20%20%7Ba%3A%201%7D%2C%0A%20%20%7Ba%3A%202%7D%2C%0A%20%20%7Ba%3A%203%7D%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.sort</strong> example in Rambda REPL</a>

sort<T>(sortFn: (a: T, b: T) => number, list: T[]): T[];
sort<T>(sortFn: (a: T, b: T) => number): (list: T[]) => T[];

import { cloneList } from './_internals/cloneList.js'

export function sort(sortFn, list){
  if (arguments.length === 1) return _list => sort(sortFn, _list)

  return cloneList(list).sort(sortFn)
}

import { sort } from './sort.js'

const fn = (a, b) => a > b ? 1 : -1

test('sort', () => {
  expect(sort((a, b) => a - b)([ 2, 3, 1 ])).toEqual([ 1, 2, 3 ])
})

test('it doesn\'t mutate', () => {
  const list = [ 'foo', 'bar', 'baz' ]

  expect(sort(fn, list)).toEqual([ 'bar', 'baz', 'foo' ])

  expect(list[ 0 ]).toBe('foo')
  expect(list[ 1 ]).toBe('bar')
  expect(list[ 2 ]).toBe('baz')
})

import {sort} from 'rambda'

const list = [3, 0, 5, 2, 1]

function sortFn(a: number, b: number): number {
  return a > b ? 1 : -1
}

describe('R.sort', () => {
  it('happy', () => {
    const result = sort(sortFn, list)
    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = sort(sortFn)(list)
    result // $ExpectType number[]
  })
})

sortBy

sortBy<T>(sortFn: (a: T) => Ord, list: T[]): T[]

It returns copy of list sorted by sortFn function, where sortFn function returns a value to compare, i.e. it doesn't need to return only -1, 0 or 1.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%0A%20%20%7Ba%3A%202%7D%2C%0A%20%20%7Ba%3A%203%7D%2C%0A%20%20%7Ba%3A%201%7D%0A%5D%0Aconst%20sortFn%20%3D%20x%20%3D%3E%20x.a%0A%0Aconst%20result%20%3D%20R.sortBy(sortFn%2C%20list)%0Aconst%20expected%20%3D%20%5B%0A%20%20%7Ba%3A%201%7D%2C%0A%20%20%7Ba%3A%202%7D%2C%0A%20%20%7Ba%3A%203%7D%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.sortBy</strong> example in Rambda REPL</a>

sortBy<T>(sortFn: (a: T) => Ord, list: T[]): T[];
sortBy<T>(sortFn: (a: T) => Ord): (list: T[]) => T[];
sortBy(sortFn: (a: any) => Ord): <T>(list: T[]) => T[];

import { cloneList } from './_internals/cloneList.js'

export function sortBy(sortFn, list){
  if (arguments.length === 1) return _list => sortBy(sortFn, _list)

  const clone = cloneList(list)

  return clone.sort((a, b) => {
    const aSortResult = sortFn(a)
    const bSortResult = sortFn(b)

    if (aSortResult === bSortResult) return 0

    return aSortResult < bSortResult ? -1 : 1
  })
}

import { compose } from './compose.js'
import { prop } from './prop.js'
import { sortBy } from './sortBy.js'
import { toLower } from './toLower.js'

test('happy', () => {
  const input = [ { a : 2 }, { a : 1 }, { a : 1 }, { a : 3 } ]
  const expected = [ { a : 1 }, { a : 1 }, { a : 2 }, { a : 3 } ]

  const result = sortBy(x => x.a)(input)
  expect(result).toEqual(expected)
})

test('with compose', () => {
  const alice = {
    name : 'ALICE',
    age  : 101,
  }
  const bob = {
    name : 'Bob',
    age  : -10,
  }
  const clara = {
    name : 'clara',
    age  : 314.159,
  }
  const people = [ clara, bob, alice ]
  const sortByNameCaseInsensitive = sortBy(compose(toLower, prop('name')))

  expect(sortByNameCaseInsensitive(people)).toEqual([ alice, bob, clara ])
})

import {sortBy, pipe} from 'rambda'

interface Input {
  a: number,
}

describe('R.sortBy', () => {
  it('passing type to sort function', () => {
    function fn(x: any): number {
      return x.a
    }
    function fn2(x: Input): number {
      return x.a
    }

    const input = [{a: 2}, {a: 1}, {a: 0}]
    const result = sortBy(fn, input)
    const curriedResult = sortBy(fn2)(input)

    result // $ExpectType { a: number; }[]
    curriedResult // $ExpectType Input[]
    result[0].a // $ExpectType number
    curriedResult[0].a // $ExpectType number
  })
  it('passing type to sort function and list', () => {
    function fn(x: Input): number {
      return x.a
    }

    const input: Input[] = [{a: 2}, {a: 1}, {a: 0}]
    const result = sortBy(fn, input)
    const curriedResult = sortBy(fn)(input)

    result // $ExpectType Input[]
    curriedResult // $ExpectType Input[]
    result[0].a // $ExpectType number
  })
  it('with R.pipe', () => {
    interface Obj {
      value: number,
    }
    const fn = pipe(sortBy<Obj>(x => x.value))

    const result = fn([{value: 1}, {value: 2}])
    result // $ExpectType Obj[]
  })
})

sortWith

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.sortWith(%5B%0A%20%20%20%20(a%2C%20b)%20%3D%3E%20a.a%20%3D%3D%3D%20b.a%20%3F%200%20%3A%20a.a%20%3E%20b.a%20%3F%201%20%3A%20-1%2C%0A%20%20%20%20(a%2C%20b)%20%3D%3E%20a.b%20%3D%3D%3D%20b.b%20%3F%200%20%3A%20a.b%20%3E%20b.b%20%3F%201%20%3A%20-1%2C%0A%5D%2C%20%5B%0A%20%20%7Ba%3A%201%2C%20b%3A%202%7D%2C%0A%20%20%7Ba%3A%202%2C%20b%3A%201%7D%2C%0A%20%20%7Ba%3A%202%2C%20b%3A%202%7D%2C%0A%20%20%7Ba%3A%201%2C%20b%3A%201%7D%2C%0A%5D)%0Aconst%20expected%20%3D%20%5B%0A%20%20%7Ba%3A%201%2C%20b%3A%201%7D%2C%0A%20%20%7Ba%3A%201%2C%20b%3A%202%7D%2C%0A%20%20%7Ba%3A%202%2C%20b%3A%201%7D%2C%0A%20%20%7Ba%3A%202%2C%20b%3A%202%7D%2C%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.sortWith</strong> example in Rambda REPL</a>

split

split(separator: string | RegExp): (str: string) => string[]

Curried version of String.prototype.split

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20str%20%3D%20'foo%7Cbar%7Cbaz'%0Aconst%20separator%20%3D%20'%7C'%0Aconst%20result%20%3D%20R.split(separator%2C%20str)%0A%2F%2F%20%3D%3E%20%5B%20'foo'%2C%20'bar'%2C%20'baz'%20%5D">Try this <strong>R.split</strong> example in Rambda REPL</a>

split(separator: string | RegExp): (str: string) => string[];
split(separator: string | RegExp, str: string): string[];

export function split(separator, str){
  if (arguments.length === 1) return _str => split(separator, _str)

  return str.split(separator)
}

import { split } from './split.js'

const str = 'foo|bar|baz'
const splitChar = '|'
const expected = [ 'foo', 'bar', 'baz' ]

test('happy', () => {
  expect(split(splitChar, str)).toEqual(expected)
})

test('curried', () => {
  expect(split(splitChar)(str)).toEqual(expected)
})

import {split} from 'rambda'

const str = 'foo|bar|baz'
const splitChar = '|'

describe('R.split', () => {
  it('happy', () => {
    const result = split(splitChar, str)

    result // $ExpectType string[]
  })
  it('curried', () => {
    const result = split(splitChar)(str)

    result // $ExpectType string[]
  })
})

splitAt

splitAt<T>(index: number, input: T[]): [T[], T[]]

It splits string or array at a given index.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%201%2C%202%2C%203%20%5D%0Aconst%20result%20%3D%20R.splitAt(2%2C%20list)%0A%2F%2F%20%3D%3E%20%5B%5B%201%2C%202%20%5D%2C%20%5B%203%20%5D%5D">Try this <strong>R.splitAt</strong> example in Rambda REPL</a>

splitAt<T>(index: number, input: T[]): [T[], T[]];
splitAt(index: number, input: string): [string, string];
splitAt(index: number): {
    <T>(input: T[]): [T[], T[]];
    (input: string): [string, string];
};

import { isArray } from './_internals/isArray.js'
import { drop } from './drop.js'
import { maybe } from './maybe.js'
import { take } from './take.js'

export function splitAt(index, input){
  if (arguments.length === 1){
    return _list => splitAt(index, _list)
  }
  if (!input) throw new TypeError(`Cannot read property 'slice' of ${ input }`)

  if (!isArray(input) && typeof input !== 'string') return [ [], [] ]

  const correctIndex = maybe(
    index < 0,
    input.length + index < 0 ? 0 : input.length + index,
    index
  )

  return [ take(correctIndex, input), drop(correctIndex, input) ]
}

import { splitAt as splitAtRamda } from 'ramda'

import { splitAt } from './splitAt.js'

const list = [ 1, 2, 3 ]
const str = 'foo bar'

test('with array', () => {
  const result = splitAt(2, list)
  expect(result).toEqual([ [ 1, 2 ], [ 3 ] ])
})

test('with array - index is negative number', () => {
  const result = splitAt(-6, list)
  expect(result).toEqual([ [], list ])
})

test('with array - index is out of scope', () => {
  const result = splitAt(4, list)
  expect(result).toEqual([ [ 1, 2, 3 ], [] ])
})

test('with string', () => {
  const result = splitAt(4, str)
  expect(result).toEqual([ 'foo ', 'bar' ])
})

test('with string - index is negative number', () => {
  const result = splitAt(-2, str)
  expect(result).toEqual([ 'foo b', 'ar' ])
})

test('with string - index is out of scope', () => {
  const result = splitAt(10, str)
  expect(result).toEqual([ str, '' ])
})

test('with array - index is out of scope', () => {
  const result = splitAt(4)(list)
  expect(result).toEqual([ [ 1, 2, 3 ], [] ])
})

const badInputs = [ 1, true, /foo/g, {} ]
const throwingBadInputs = [ null, undefined ]

test('with bad inputs', () => {
  throwingBadInputs.forEach(badInput => {
    expect(() => splitAt(1, badInput)).toThrowWithMessage(TypeError,
      `Cannot read property 'slice' of ${ badInput }`)
    expect(() => splitAtRamda(1, badInput)).toThrowWithMessage(TypeError,
      `Cannot read properties of ${ badInput } (reading 'slice')`)
  })

  badInputs.forEach(badInput => {
    const result = splitAt(1, badInput)
    const ramdaResult = splitAtRamda(1, badInput)
    expect(result).toEqual(ramdaResult)
  })
})

import {splitAt} from 'rambda'

const index = 1
const str = 'foo'
const list = [1, 2, 3]

describe('R.splitAt with array', () => {
  it('happy', () => {
    const result = splitAt(index, list)

    result // $ExpectType [number[], number[]]
  })
  it('curried', () => {
    const result = splitAt(index)(list)

    result // $ExpectType [number[], number[]]
  })
})

describe('R.splitAt with string', () => {
  it('happy', () => {
    const result = splitAt(index, str)

    result // $ExpectType [string, string]
  })
  it('curried', () => {
    const result = splitAt(index)(str)

    result // $ExpectType [string, string]
  })
})

splitEvery

splitEvery<T>(sliceLength: number, input: T[]): (T[])[]

It splits input into slices of sliceLength.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.splitEvery(2%2C%20%5B1%2C%202%2C%203%5D)%2C%20%0A%20%20R.splitEvery(3%2C%20'foobar')%20%0A%5D%0A%0Aconst%20expected%20%3D%20%5B%0A%20%20%5B%5B1%2C%202%5D%2C%20%5B3%5D%5D%2C%0A%20%20%5B'foo'%2C%20'bar'%5D%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.splitEvery</strong> example in Rambda REPL</a>

splitEvery<T>(sliceLength: number, input: T[]): (T[])[];
splitEvery(sliceLength: number, input: string): string[];
splitEvery(sliceLength: number): {
  (input: string): string[];
  <T>(input: T[]): (T[])[];
};

export function splitEvery(sliceLength, listOrString){
  if (arguments.length === 1){
    return _listOrString => splitEvery(sliceLength, _listOrString)
  }

  if (sliceLength < 1){
    throw new Error('First argument to splitEvery must be a positive integer')
  }

  const willReturn = []
  let counter = 0

  while (counter < listOrString.length){
    willReturn.push(listOrString.slice(counter, counter += sliceLength))
  }

  return willReturn
}

import { splitEvery } from './splitEvery.js'

test('happy', () => {
  expect(splitEvery(3, [ 1, 2, 3, 4, 5, 6, 7 ])).toEqual([
    [ 1, 2, 3 ],
    [ 4, 5, 6 ],
    [ 7 ],
  ])

  expect(splitEvery(3)('foobarbaz')).toEqual([ 'foo', 'bar', 'baz' ])
})

test('with bad input', () => {
  expect(() =>
    expect(splitEvery(0)('foo')).toEqual([ 'f', 'o', 'o' ])).toThrowErrorMatchingInlineSnapshot('"First argument to splitEvery must be a positive integer"')
})

import {splitEvery} from 'rambda'

const list = [1, 2, 3, 4, 5, 6, 7]

describe('R.splitEvery', () => {
  it('happy', () => {
    const result = splitEvery(3, list)

    result // $ExpectType number[][]
  })
  it('curried', () => {
    const result = splitEvery(3)(list)

    result // $ExpectType number[][]
  })
})

splitWhen

splitWhen<T, U>(predicate: Predicate<T>, list: U[]): (U[])[]

It splits list to two arrays according to a predicate function.

The first array contains all members of list before predicate returns true.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%201%2C%202%5D%0Aconst%20result%20%3D%20R.splitWhen(R.equals(2)%2C%20list)%0A%2F%2F%20%3D%3E%20%5B%5B1%5D%2C%20%5B2%2C%201%2C%202%5D%5D">Try this <strong>R.splitWhen</strong> example in Rambda REPL</a>

splitWhen<T, U>(predicate: Predicate<T>, list: U[]): (U[])[];
splitWhen<T>(predicate: Predicate<T>): <U>(list: U[]) => (U[])[];

export function splitWhen(predicate, input){
  if (arguments.length === 1){
    return _input => splitWhen(predicate, _input)
  }
  if (!input)
    throw new TypeError(`Cannot read property 'length' of ${ input }`)

  const preFound = []
  const postFound = []
  let found = false
  let counter = -1

  while (counter++ < input.length - 1){
    if (found){
      postFound.push(input[ counter ])
    } else if (predicate(input[ counter ])){
      postFound.push(input[ counter ])
      found = true
    } else {
      preFound.push(input[ counter ])
    }
  }

  return [ preFound, postFound ]
}

import { splitWhen as splitWhenRamda } from 'ramda'

import { equals } from './equals.js'
import { splitWhen } from './splitWhen.js'

const list = [ 1, 2, 1, 2 ]

test('happy', () => {
  const result = splitWhen(equals(2), list)
  expect(result).toEqual([ [ 1 ], [ 2, 1, 2 ] ])
})

test('when predicate returns false', () => {
  const result = splitWhen(equals(3))(list)
  expect(result).toEqual([ list, [] ])
})

const badInputs = [ 1, true, /foo/g, {} ]
const throwingBadInputs = [ null, undefined ]

test('with bad inputs', () => {
  throwingBadInputs.forEach(badInput => {
    expect(() => splitWhen(equals(2), badInput)).toThrowWithMessage(TypeError,
      `Cannot read property 'length' of ${ badInput }`)
    expect(() => splitWhenRamda(equals(2), badInput)).toThrowWithMessage(TypeError,
      `Cannot read properties of ${ badInput } (reading 'length')`)
  })

  badInputs.forEach(badInput => {
    const result = splitWhen(equals(2), badInput)
    const ramdaResult = splitWhenRamda(equals(2), badInput)
    expect(result).toEqual(ramdaResult)
  })
})

import {splitWhen} from 'rambda'

const list = [1, 2, 1, 2]
const predicate = (x: number) => x === 2

describe('R.splitWhen', () => {
  it('happy', () => {
    const result = splitWhen(predicate, list)

    result // $ExpectType number[][]
  })
  it('curried', () => {
    const result = splitWhen(predicate)(list)

    result // $ExpectType number[][]
  })
})

startsWith

startsWith<T extends string>(question: T, input: string): boolean

When iterable is a string, then it behaves as String.prototype.startsWith. When iterable is a list, then it uses R.equals to determine if the target list starts in the same way as the given target.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20str%20%3D%20'foo-bar'%0Aconst%20list%20%3D%20%5B%7Ba%3A1%7D%2C%20%7Ba%3A2%7D%2C%20%7Ba%3A3%7D%5D%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.startsWith('foo'%2C%20str)%2C%0A%20%20R.startsWith(%5B%7Ba%3A1%7D%2C%20%7Ba%3A2%7D%5D%2C%20list)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20true%5D">Try this <strong>R.startsWith</strong> example in Rambda REPL</a>

startsWith<T extends string>(question: T, input: string): boolean;
startsWith<T extends string>(question: T): (input: string) => boolean;
startsWith<T>(question: T[], input: T[]): boolean;
startsWith<T>(question: T[]): (input: T[]) => boolean;

import { isArray } from './_internals/isArray.js'
import { equals } from './equals.js'

export function startsWith(question, iterable){
  if (arguments.length === 1)
    return _iterable => startsWith(question, _iterable)

  if (typeof iterable === 'string'){
    return iterable.startsWith(question)
  }
  if (!isArray(question)) return false

  let correct = true
  const filtered = question.filter((x, index) => {
    if (!correct) return false
    const result = equals(x, iterable[ index ])
    if (!result) correct = false

    return result
  })

  return filtered.length === question.length
}

import { startsWith as startsWithRamda } from 'ramda'

import { compareCombinations } from './_internals/testUtils.js'
import { possibleIterables, possibleTargets } from './endsWith.spec.js'
import { startsWith } from './startsWith.js'

test('with string', () => {
  expect(startsWith('foo', 'foo-bar')).toBeTrue()
  expect(startsWith('baz')('foo-bar')).toBeFalse()
})

test('use R.equals with array', () => {
  const list = [ { a : 1 }, { a : 2 }, { a : 3 } ]
  expect(startsWith({ a : 1 }, list)).toBeFalse()
  expect(startsWith([ { a : 1 } ], list)).toBeTrue()
  expect(startsWith([ { a : 1 }, { a : 2 } ], list)).toBeTrue()
  expect(startsWith(list, list)).toBeTrue()
  expect(startsWith([ { a : 2 } ], list)).toBeFalse()
})

describe('brute force', () => {
  compareCombinations({
    fn          : startsWith,
    fnRamda     : startsWithRamda,
    firstInput  : possibleTargets,
    secondInput : possibleIterables,
    callback    : errorsCounters => {
      expect(errorsCounters).toMatchInlineSnapshot(`
        {
          "ERRORS_MESSAGE_MISMATCH": 0,
          "ERRORS_TYPE_MISMATCH": 0,
          "RESULTS_MISMATCH": 0,
          "SHOULD_NOT_THROW": 0,
          "SHOULD_THROW": 0,
          "TOTAL_TESTS": 32,
        }
      `)
    },
  })
})

import {startsWith} from 'rambda'

describe('R.startsWith - array', () => {
  const question = [{a: 1}]
  const iterable = [{a: 1}, {a: 2}]
  it('happy', () => {
    const result = startsWith(question, iterable)
    result // $ExpectType boolean
  })
  it('curried', () => {
    const result = startsWith(question)(iterable)
    result // $ExpectType boolean
  })
})

describe('R.startsWith - string', () => {
  const question = 'foo'
  const iterable = 'foo bar'
  it('happy', () => {
    const result = startsWith(question, iterable)
    result // $ExpectType boolean
  })
  it('curried', () => {
    const result = startsWith(question)(iterable)
    result // $ExpectType boolean
  })
})

subtract

Curried version of x - y

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20x%20%3D%203%0Aconst%20y%20%3D%201%0A%0Aconst%20result%20%3D%20R.subtract(x%2C%20y)%20%0A%2F%2F%20%3D%3E%202">Try this <strong>R.subtract</strong> example in Rambda REPL</a>

sum

sum(list: number[]): number

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.sum(%5B1%2C%202%2C%203%2C%204%2C%205%5D)%20%0A%2F%2F%20%3D%3E%2015">Try this <strong>R.sum</strong> example in Rambda REPL</a>

sum(list: number[]): number;

export function sum(list){
  return list.reduce((prev, current) => prev + current, 0)
}

import { sum } from './sum.js'

test('happy', () => {
  expect(sum([ 1, 2, 3, 4, 5 ])).toBe(15)
})

swap

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.swap(1%2C%202%2C%20%5B1%2C%202%2C%203%5D)%0A%2F%2F%20%3D%3E%20%5B1%2C%203%2C%202%5D">Try this <strong>R.swap</strong> example in Rambda REPL</a>

symmetricDifference

symmetricDifference<T>(x: T[], y: T[]): T[]

It returns a merged list of x and y with all equal elements removed.

R.equals is used to determine equality.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20x%20%3D%20%5B%201%2C%202%2C%203%2C%204%20%5D%0Aconst%20y%20%3D%20%5B%203%2C%204%2C%205%2C%206%20%5D%0A%0Aconst%20result%20%3D%20R.symmetricDifference(x%2C%20y)%0A%2F%2F%20%3D%3E%20%5B%201%2C%202%2C%205%2C%206%20%5D">Try this <strong>R.symmetricDifference</strong> example in Rambda REPL</a>

symmetricDifference<T>(x: T[], y: T[]): T[];
symmetricDifference<T>(x: T[]): <T>(y: T[]) => T[];

import { concat } from './concat.js'
import { filter } from './filter.js'
import { includes } from './includes.js'

export function symmetricDifference(x, y){
  if (arguments.length === 1){
    return _y => symmetricDifference(x, _y)
  }

  return concat(filter(value => !includes(value, y), x),
    filter(value => !includes(value, x), y))
}

import { symmetricDifference } from './symmetricDifference.js'

test('symmetricDifference', () => {
  const list1 = [ 1, 2, 3, 4 ]
  const list2 = [ 3, 4, 5, 6 ]
  expect(symmetricDifference(list1)(list2)).toEqual([ 1, 2, 5, 6 ])

  expect(symmetricDifference([], [])).toEqual([])
})

test('symmetricDifference with objects', () => {
  const list1 = [ { id : 1 }, { id : 2 }, { id : 3 }, { id : 4 } ]
  const list2 = [ { id : 3 }, { id : 4 }, { id : 5 }, { id : 6 } ]
  expect(symmetricDifference(list1)(list2)).toEqual([
    { id : 1 },
    { id : 2 },
    { id : 5 },
    { id : 6 },
  ])
})

import {symmetricDifference} from 'rambda'

describe('R.symmetricDifference', () => {
  it('happy', () => {
    const list1 = [1, 2, 3, 4]
    const list2 = [3, 4, 5, 6]
    const result = symmetricDifference(list1, list2)

    result // $ExpectType number[]
  })

  it('curried', () => {
    const list1 = [{id: 1}, {id: 2}, {id: 3}, {id: 4}]
    const list2 = [{id: 3}, {id: 4}, {id: 5}, {id: 6}]
    const result = symmetricDifference(list1)(list2)

    result // $ExpectType { id: number; }[]
  })
})

T

T(): boolean

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.T()%20%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.T</strong> example in Rambda REPL</a>

T(): boolean;

export function T(){
  return true
}

tail

tail<T extends unknown[]>(input: T): T extends [any, ...infer U] ? U : [...T]

It returns all but the first element of input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20R.tail(%5B1%2C%202%2C%203%5D)%2C%20%20%0A%20%20R.tail('foo')%20%0A%5D%0A%2F%2F%20%3D%3E%20%5B%5B2%2C%203%5D%2C%20'oo'%5D">Try this <strong>R.tail</strong> example in Rambda REPL</a>

tail<T extends unknown[]>(input: T): T extends [any, ...infer U] ? U : [...T];
tail(input: string): string;

import { drop } from './drop.js'

export function tail(listOrString){
  return drop(1, listOrString)
}

import { tail } from './tail.js'

test('tail', () => {
  expect(tail([ 1, 2, 3 ])).toEqual([ 2, 3 ])
  expect(tail([ 1, 2 ])).toEqual([ 2 ])
  expect(tail([ 1 ])).toEqual([])
  expect(tail([])).toEqual([])

  expect(tail('abc')).toBe('bc')
  expect(tail('ab')).toBe('b')
  expect(tail('a')).toBe('')
  expect(tail('')).toBe('')
})

import {tail} from 'rambda'

describe('R.tail', () => {
  it('with string', () => {
    const result = tail('foo')

    result // $ExpectType string
  })
  it('with list - one type', () => {
    const result = tail([1, 2, 3])

    result // $ExpectType number[]
  })
  it('with list - mixed types', () => {
    const result = tail(['foo', 'bar', 1, 2, 3])

    result // $ExpectType (string | number)[]
  })
})

take

take<T>(howMany: number, input: T[]): T[]

It returns the first howMany elements of input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20howMany%20%3D%202%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.take(howMany%2C%20%5B1%2C%202%2C%203%5D)%2C%0A%20%20R.take(howMany%2C%20'foobar')%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5B%5B1%2C%202%5D%2C%20'fo'%5D">Try this <strong>R.take</strong> example in Rambda REPL</a>

take<T>(howMany: number, input: T[]): T[];
take(howMany: number, input: string): string;
take<T>(howMany: number): {
  <T>(input: T[]): T[];
  (input: string): string;
};

import baseSlice from './_internals/baseSlice.js'

export function take(howMany, listOrString){
  if (arguments.length === 1)
    return _listOrString => take(howMany, _listOrString)
  if (howMany < 0) return listOrString.slice()
  if (typeof listOrString === 'string') return listOrString.slice(0, howMany)

  return baseSlice(
    listOrString, 0, howMany
  )
}

import { take } from './take.js'

test('happy', () => {
  const arr = [ 'foo', 'bar', 'baz' ]

  expect(take(1, arr)).toEqual([ 'foo' ])

  expect(arr).toEqual([ 'foo', 'bar', 'baz' ])

  expect(take(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar' ])
  expect(take(3, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ])
  expect(take(4, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ])
  expect(take(3)('rambda')).toBe('ram')
})

test('with negative index', () => {
  expect(take(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
  expect(take(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
})

test('with zero index', () => {
  expect(take(0, [ 1, 2, 3 ])).toEqual([])
})

import {take} from 'rambda'

const list = [1, 2, 3, 4]
const str = 'foobar'
const howMany = 2

describe('R.take - array', () => {
  it('happy', () => {
    const result = take(howMany, list)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = take(howMany)(list)

    result // $ExpectType number[]
  })
})

describe('R.take - string', () => {
  it('happy', () => {
    const result = take(howMany, str)

    result // $ExpectType string
  })
  it('curried', () => {
    const result = take(howMany)(str)

    result // $ExpectType string
  })
})

takeLast

takeLast<T>(howMany: number, input: T[]): T[]

It returns the last howMany elements of input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20howMany%20%3D%202%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.takeLast(howMany%2C%20%5B1%2C%202%2C%203%5D)%2C%0A%20%20R.takeLast(howMany%2C%20'foobar')%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5B%5B2%2C%203%5D%2C%20'ar'%5D">Try this <strong>R.takeLast</strong> example in Rambda REPL</a>

takeLast<T>(howMany: number, input: T[]): T[];
takeLast(howMany: number, input: string): string;
takeLast<T>(howMany: number): {
  <T>(input: T[]): T[];
  (input: string): string;
};

import baseSlice from './_internals/baseSlice.js'

export function takeLast(howMany, listOrString){
  if (arguments.length === 1)
    return _listOrString => takeLast(howMany, _listOrString)

  const len = listOrString.length
  if (howMany < 0) return listOrString.slice()
  let numValue = howMany > len ? len : howMany

  if (typeof listOrString === 'string')
    return listOrString.slice(len - numValue)

  numValue = len - numValue

  return baseSlice(
    listOrString, numValue, len
  )
}

import { takeLast } from './takeLast.js'

test('with arrays', () => {
  expect(takeLast(1, [ 'foo', 'bar', 'baz' ])).toEqual([ 'baz' ])

  expect(takeLast(2)([ 'foo', 'bar', 'baz' ])).toEqual([ 'bar', 'baz' ])

  expect(takeLast(3, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ])

  expect(takeLast(4, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ])

  expect(takeLast(10, [ 'foo', 'bar', 'baz' ])).toEqual([ 'foo', 'bar', 'baz' ])
})

test('with strings', () => {
  expect(takeLast(3, 'rambda')).toBe('bda')

  expect(takeLast(7, 'rambda')).toBe('rambda')
})

test('with negative index', () => {
  expect(takeLast(-1, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
  expect(takeLast(-Infinity, [ 1, 2, 3 ])).toEqual([ 1, 2, 3 ])
})

import {takeLast} from 'rambda'

const list = [1, 2, 3, 4]
const str = 'foobar'
const howMany = 2

describe('R.takeLast - array', () => {
  it('happy', () => {
    const result = takeLast(howMany, list)

    result // $ExpectType number[]
  })
  it('curried', () => {
    const result = takeLast(howMany)(list)

    result // $ExpectType number[]
  })
})

describe('R.takeLast - string', () => {
  it('happy', () => {
    const result = takeLast(howMany, str)

    result // $ExpectType string
  })
  it('curried', () => {
    const result = takeLast(howMany)(str)

    result // $ExpectType string
  })
})

takeLastWhile

takeLastWhile(predicate: (x: string) => boolean, input: string): string

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.takeLastWhile(%0A%20%20x%20%3D%3E%20x%20%3E%202%2C%0A%20%20%5B1%2C%202%2C%203%2C%204%5D%0A)%0A%2F%2F%20%3D%3E%20%5B3%2C%204%5D">Try this <strong>R.takeLastWhile</strong> example in Rambda REPL</a>

takeLastWhile(predicate: (x: string) => boolean, input: string): string;
takeLastWhile(predicate: (x: string) => boolean): (input: string) => string;
takeLastWhile<T>(predicate: (x: T) => boolean, input: T[]): T[];
takeLastWhile<T>(predicate: (x: T) => boolean): <T>(input: T[]) => T[];

import { isArray } from './_internals/isArray.js'

export function takeLastWhile(predicate, input){
  if (arguments.length === 1){
    return _input => takeLastWhile(predicate, _input)
  }
  if (input.length === 0) return input

  const toReturn = []
  let counter = input.length

  while (counter){
    const item = input[ --counter ]
    if (!predicate(item)){
      break
    }
    toReturn.push(item)
  }

  return isArray(input) ? toReturn.reverse() : toReturn.reverse().join('')
}

import { takeLastWhile } from './takeLastWhile.js'
const assert = require('assert')

const list = [ 1, 2, 3, 4 ]

test('happy', () => {
  const predicate = x => x > 2
  const result = takeLastWhile(predicate, list)
  expect(result).toEqual([ 3, 4 ])
})

test('predicate is always true', () => {
  const predicate = () => true
  const result = takeLastWhile(predicate)(list)
  expect(result).toEqual(list)
})

test('predicate is always false', () => {
  const predicate = () => false
  const result = takeLastWhile(predicate, list)
  expect(result).toEqual([])
})

test('with string', () => {
  const result = takeLastWhile(x => x !== 'F', 'FOOBAR')
  expect(result).toBe('OOBAR')
})

import {takeLastWhile} from 'rambda'

const list = [1, 2, 3]
const str = 'FOO'

describe('R.takeLastWhile', () => {
  it('with array', () => {
    const result = takeLastWhile(x => x > 1, list)

    result // $ExpectType number[]
  })
  it('with array - curried', () => {
    const result = takeLastWhile(x => x > 1, list)

    result // $ExpectType number[]
  })
  it('with string', () => {
    const result = takeLastWhile(x => x !== 'F', str)

    result // $ExpectType string
  })
  it('with string - curried', () => {
    const result = takeLastWhile(x => x !== 'F')(str)

    result // $ExpectType string
  })
})

takeWhile

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20predicate%20%3D%20x%20%3D%3E%20x%20%3C%203%0A%0Aconst%20result%20%3D%20R.takeWhile(predicate%2C%20list)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%5D">Try this <strong>R.takeWhile</strong> example in Rambda REPL</a>

tap

tap<T>(fn: (x: T) => void, input: T): T

It applies function fn to input x and returns x.

One use case is debugging in the middle of R.compose.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%202%2C%203%5D%0A%0AR.compose(%0A%20%20R.map(x%20%3D%3E%20x%20*%202)%0A%20%20R.tap(console.log)%2C%0A%20%20R.filter(x%20%3D%3E%20x%20%3E%201)%0A)(list)%0A%2F%2F%20%3D%3E%20%602%60%20and%20%603%60%20will%20be%20logged">Try this <strong>R.tap</strong> example in Rambda REPL</a>

tap<T>(fn: (x: T) => void, input: T): T;
tap<T>(fn: (x: T) => void): (input: T) => T;

export function tap(fn, x){
  if (arguments.length === 1) return _x => tap(fn, _x)

  fn(x)

  return x
}

import { tap } from './tap.js'

test('tap', () => {
  let a = 1
  const sayX = x => a = x

  expect(tap(sayX, 100)).toBe(100)
  expect(tap(sayX)(100)).toBe(100)
  expect(a).toBe(100)
})

import {tap, pipe} from 'rambda'

describe('R.tap', () => {
  it('happy', () => {
    pipe(
      tap(x => {
        x // $ExpectType number[]
      }),
      (x: number[]) => x.length
    )([1, 2])
  })
})

test

test(regExpression: RegExp): (str: string) => boolean

It determines whether str matches regExpression.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.test(%2F%5Ef%2F%2C%20'foo')%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.test</strong> example in Rambda REPL</a>

test(regExpression: RegExp): (str: string) => boolean;
test(regExpression: RegExp, str: string): boolean;

export function test(pattern, str){
  if (arguments.length === 1) return _str => test(pattern, _str)

  if (typeof pattern === 'string'){
    throw new TypeError(`R.test requires a value of type RegExp as its first argument; received "${ pattern }"`)
  }

  return str.search(pattern) !== -1
}

import { test as testMethod } from './test.js'

test('happy', () => {
  expect(testMethod(/^x/, 'xyz')).toBeTrue()

  expect(testMethod(/^y/)('xyz')).toBeFalse()
})

test('throws if first argument is not regex', () => {
  expect(() => testMethod('foo', 'bar')).toThrowErrorMatchingInlineSnapshot('"R.test requires a value of type RegExp as its first argument; received "foo""')
})

import {test} from 'rambda'

const input = 'foo   '
const regex = /foo/

describe('R.test', () => {
  it('happy', () => {
    const result = test(regex, input)

    result // $ExpectType boolean
  })
  it('curried', () => {
    const result = test(regex)(input)

    result // $ExpectType boolean
  })
})

times

times<T>(fn: (i: number) => T, howMany: number): T[]

It returns the result of applying function fn over members of range array.

The range array includes numbers between 0 and howMany(exclusive).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20x%20%3D%3E%20x%20*%202%0Aconst%20howMany%20%3D%205%0A%0Aconst%20result%20%3D%20R.times(fn%2C%20howMany)%0A%2F%2F%20%3D%3E%20%5B0%2C%202%2C%204%2C%206%2C%208%5D">Try this <strong>R.times</strong> example in Rambda REPL</a>

times<T>(fn: (i: number) => T, howMany: number): T[];
times<T>(fn: (i: number) => T): (howMany: number) => T[];

import { isInteger } from './_internals/isInteger.js'
import { map } from './map.js'
import { range } from './range.js'

export function times(fn, howMany){
  if (arguments.length === 1) return _howMany => times(fn, _howMany)
  if (!isInteger(howMany) || howMany < 0){
    throw new RangeError('n must be an integer')
  }

  return map(fn, range(0, howMany))
}

import assert from 'assert'

import { identity } from './identity.js'
import { times } from './times.js'

test('happy', () => {
  const result = times(identity, 5)

  expect(result).toEqual([ 0, 1, 2, 3, 4 ])
})

test('with bad input', () => {
  assert.throws(() => {
    times(3)('cheers!')
  }, RangeError)
  assert.throws(() => {
    times(identity, -1)
  }, RangeError)
})

test('curry', () => {
  const result = times(identity)(5)

  expect(result).toEqual([ 0, 1, 2, 3, 4 ])
})

import {times, identity} from 'rambda'

describe('R.times', () => {
  it('happy', () => {
    const result = times(identity, 5)
    result // $ExpectType number[]
  })
})

toLower

toLower<S extends string>(str: S): Lowercase<S>

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.toLower('FOO')%0A%2F%2F%20%3D%3E%20'foo'">Try this <strong>R.toLower</strong> example in Rambda REPL</a>

toLower<S extends string>(str: S): Lowercase<S>;
toLower(str: string): string;

export function toLower(str){
  return str.toLowerCase()
}

import { toLower } from './toLower.js'

test('toLower', () => {
  expect(toLower('FOO|BAR|BAZ')).toBe('foo|bar|baz')
})

toPairs

toPairs<O extends object, K extends Extract<keyof O, string | number>>(obj: O): Array<{ [key in K]: [`${key}`, O[key]] }[K]>

It transforms an object to a list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%7B%0A%20%20a%20%3A%201%2C%0A%20%20b%20%3A%202%2C%0A%20%20c%20%3A%20%5B%203%2C%204%20%5D%2C%0A%7D%0Aconst%20expected%20%3D%20%5B%20%5B%20'a'%2C%201%20%5D%2C%20%5B%20'b'%2C%202%20%5D%2C%20%5B%20'c'%2C%20%5B%203%2C%204%20%5D%20%5D%20%5D%0A%0Aconst%20result%20%3D%20R.toPairs(list)%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.toPairs</strong> example in Rambda REPL</a>

toPairs<O extends object, K extends Extract<keyof O, string | number>>(obj: O): Array<{ [key in K]: [`${key}`, O[key]] }[K]>;
toPairs<S>(obj: Record<string | number, S>): Array<[string, S]>;

export function toPairs(obj){
  return Object.entries(obj)
}

import { toPairs } from './toPairs.js'

const obj = {
  a : 1,
  b : 2,
  c : [ 3, 4 ],
}
const expected = [
  [ 'a', 1 ],
  [ 'b', 2 ],
  [ 'c', [ 3, 4 ] ],
]

test('happy', () => {
  expect(toPairs(obj)).toEqual(expected)
})

toString

toString(x: unknown): string

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.toString(%5B1%2C%202%5D)%20%0A%2F%2F%20%3D%3E%20'1%2C2'">Try this <strong>R.toString</strong> example in Rambda REPL</a>

toString(x: unknown): string;

export function toString(x){
  return x.toString()
}

import { toString } from './toString.js'

test('happy', () => {
  expect(toString([ 1, 2, 3 ])).toBe('1,2,3')
})

toUpper

toUpper<S extends string>(str: S): Uppercase<S>

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.toUpper('foo')%0A%2F%2F%20%3D%3E%20'FOO'">Try this <strong>R.toUpper</strong> example in Rambda REPL</a>

toUpper<S extends string>(str: S): Uppercase<S>;
toUpper(str: string): string;

export function toUpper(str){
  return str.toUpperCase()
}

import { toUpper } from './toUpper.js'

test('toUpper', () => {
  expect(toUpper('foo|bar|baz')).toBe('FOO|BAR|BAZ')
})

transpose

transpose<T>(list: (T[])[]): (T[])[]

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%5B10%2C%2011%5D%2C%20%5B20%5D%2C%20%5B%5D%2C%20%5B30%2C%2031%2C%2032%5D%5D%0Aconst%20expected%20%3D%20%5B%5B10%2C%2020%2C%2030%5D%2C%20%5B11%2C%2031%5D%2C%20%5B32%5D%5D%0A%0Aconst%20result%20%3D%20R.transpose(list)%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.transpose</strong> example in Rambda REPL</a>

transpose<T>(list: (T[])[]): (T[])[];

import { isArray } from './_internals/isArray.js'

export function transpose(array){
  return array.reduce((acc, el) => {
    el.forEach((nestedEl, i) =>
      isArray(acc[ i ]) ? acc[ i ].push(nestedEl) : acc.push([ nestedEl ]))

    return acc
  }, [])
}

import { transpose } from './transpose.js'

test('happy', () => {
  const input = [
    [ 'a', 1 ],
    [ 'b', 2 ],
    [ 'c', 3 ],
  ]

  expect(transpose(input)).toEqual([
    [ 'a', 'b', 'c' ],
    [ 1, 2, 3 ],
  ])
})

test('when rows are shorter', () => {
  const actual = transpose([ [ 10, 11 ], [ 20 ], [], [ 30, 31, 32 ] ])
  const expected = [ [ 10, 20, 30 ], [ 11, 31 ], [ 32 ] ]
  expect(actual).toEqual(expected)
})

test('with empty array', () => {
  expect(transpose([])).toEqual([])
})

test('array with falsy values', () => {
  const actual = transpose([
    [ true, false, undefined, null ],
    [ null, undefined, false, true ],
  ])
  const expected = [
    [ true, null ],
    [ false, undefined ],
    [ undefined, false ],
    [ null, true ],
  ]
  expect(actual).toEqual(expected)
})

import {transpose} from 'rambda'

const input = [
  ['a', 1],
  ['b', 2],
  ['c', 3],
]

describe('R.transpose', () => {
  it('happy', () => {
    const result = transpose(input)

    result // $ExpectType (string | number)[][]
  })
})

trim

trim(str: string): string

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.trim('%20%20foo%20%20')%20%0A%2F%2F%20%3D%3E%20'foo'">Try this <strong>R.trim</strong> example in Rambda REPL</a>

trim(str: string): string;

export function trim(str){
  return str.trim()
}

import { trim } from './trim.js'

test('trim', () => {
  expect(trim(' foo ')).toBe('foo')
})

tryCatch

It returns function that runs fn in try/catch block. If there was an error, then fallback is used to return the result. Note that fn can be value or asynchronous/synchronous function(unlike Ramda where fallback can only be a synchronous function).

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20x%20%3D%3E%20x.foo%0A%0Aconst%20result%20%3D%20%5B%0A%20%20R.tryCatch(fn%2C%20false)(null)%2C%0A%20%20R.tryCatch(fn%2C%20false)(%7Bfoo%3A%20'bar'%7D)%0A%5D%0A%2F%2F%20%3D%3E%20%5Bfalse%2C%20'bar'%5D">Try this <strong>R.tryCatch</strong> example in Rambda REPL</a>

type

It accepts any input and it returns its type.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.type(()%20%3D%3E%20%7B%7D)%20%2F%2F%20%3D%3E%20'Function'%0AR.type(async%20()%20%3D%3E%20%7B%7D)%20%2F%2F%20%3D%3E%20'Async'%0AR.type(%5B%5D)%20%2F%2F%20%3D%3E%20'Array'%0AR.type(%7B%7D)%20%2F%2F%20%3D%3E%20'Object'%0AR.type('foo')%20%2F%2F%20%3D%3E%20'String'%0AR.type(1)%20%2F%2F%20%3D%3E%20'Number'%0AR.type(true)%20%2F%2F%20%3D%3E%20'Boolean'%0AR.type(null)%20%2F%2F%20%3D%3E%20'Null'%0AR.type(%2F%5BA-z%5D%2F)%20%2F%2F%20%3D%3E%20'RegExp'%0AR.type('foo'*1)%20%2F%2F%20%3D%3E%20'NaN'%0A%0Aconst%20delay%20%3D%20ms%20%3D%3E%20new%20Promise(resolve%20%3D%3E%20%7B%0A%20%20setTimeout(function%20()%20%7B%0A%20%20%20%20resolve()%0A%20%20%7D%2C%20ms)%0A%7D)%0AR.type(delay)%20%2F%2F%20%3D%3E%20'Promise'">Try this <strong>R.type</strong> example in Rambda REPL</a>

unapply

unapply<T = any>(fn: (args: any[]) => T): (...args: any[]) => T

It calls a function fn with the list of values of the returned function.

R.unapply is the opposite of R.apply method.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.unapply(JSON.stringify)(1%2C%202%2C%203)%0A%2F%2F%3D%3E%20'%5B1%2C2%2C3%5D'">Try this <strong>R.unapply</strong> example in Rambda REPL</a>

unapply<T = any>(fn: (args: any[]) => T): (...args: any[]) => T;

export function unapply(fn){
  return function (...args){
    return fn.call(this, args)
  }
}

import { apply } from './apply.js'
import { converge } from './converge.js'
import { identity } from './identity.js'
import { prop } from './prop.js'
import { sum } from './sum.js'
import { unapply } from './unapply.js'

test('happy', () => {
  const fn = unapply(identity)
  expect(fn(
    1, 2, 3
  )).toEqual([ 1, 2, 3 ])
  expect(fn()).toEqual([])
})

test('returns a function which is always passed one argument', () => {
  const fn = unapply(function (){
    return arguments.length
  })
  expect(fn('x')).toBe(1)
  expect(fn('x', 'y')).toBe(1)
  expect(fn(
    'x', 'y', 'z'
  )).toBe(1)
})

test('forwards arguments to decorated function as an array', () => {
  const fn = unapply(xs => '[' + xs + ']')
  expect(fn(2)).toBe('[2]')
  expect(fn(2, 4)).toBe('[2,4]')
  expect(fn(
    2, 4, 6
  )).toBe('[2,4,6]')
})

test('returns a function with length 0', () => {
  const fn = unapply(identity)
  expect(fn).toHaveLength(0)
})

test('is the inverse of R.apply', () => {
  let a, b, c, d, e, f, g, n
  const rand = function (){
    return Math.floor(200 * Math.random()) - 100
  }

  f = Math.max
  g = unapply(apply(f))
  n = 1
  while (n <= 100){
    a = rand()
    b = rand()
    c = rand()
    d = rand()
    e = rand()
    expect(f(
      a, b, c, d, e
    )).toEqual(g(
      a, b, c, d, e
    ))
    n += 1
  }

  f = function (xs){
    return '[' + xs + ']'
  }
  g = apply(unapply(f))
  n = 1
  while (n <= 100){
    a = rand()
    b = rand()
    c = rand()
    d = rand()
    e = rand()
    expect(f([ a, b, c, d, e ])).toEqual(g([ a, b, c, d, e ]))
    n += 1
  }
})

test('it works with converge', () => {
  const fn = unapply(sum)
  const convergeFn = converge(fn, [ prop('a'), prop('b'), prop('c') ])
  const obj = {
    a : 1337,
    b : 42,
    c : 1,
  }
  const expected = 1337 + 42 + 1
  expect(convergeFn(obj)).toEqual(expected)
})

import {join, unapply, sum} from 'rambda'

describe('R.unapply', () => {
  it('happy', () => {
    const fn = unapply(sum)

    fn(1, 2, 3) // $ExpectType number
  })

  it('joins a string', () => {
    const fn = unapply(join(''))

    fn('s', 't', 'r', 'i', 'n', 'g') // $ExpectType string
  })
})

union

union<T>(x: T[], y: T[]): T[]

It takes two lists and return a new list containing a merger of both list with removed duplicates.

R.equals is used to compare for duplication.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.union(%5B1%2C2%2C3%5D%2C%20%5B3%2C4%2C5%5D)%3B%0A%2F%2F%20%3D%3E%20%5B1%2C%202%2C%203%2C%204%2C%205%5D">Try this <strong>R.union</strong> example in Rambda REPL</a>

union<T>(x: T[], y: T[]): T[];
union<T>(x: T[]): (y: T[]) => T[];

import { cloneList } from './_internals/cloneList.js'
import { includes } from './includes.js'

export function union(x, y){
  if (arguments.length === 1) return _y => union(x, _y)

  const toReturn = cloneList(x)

  y.forEach(yInstance => {
    if (!includes(yInstance, x)) toReturn.push(yInstance)
  })

  return toReturn
}

import { union } from './union.js'

test('happy', () => {
  expect(union([ 1, 2 ], [ 2, 3 ])).toEqual([ 1, 2, 3 ])
})

test('with list of objects', () => {
  const list1 = [ { a : 1 }, { a : 2 } ]
  const list2 = [ { a : 2 }, { a : 3 } ]
  const result = union(list1)(list2)
})

import {union} from 'rambda'

describe('R.union', () => {
  it('happy', () => {
    const result = union([1, 2], [2, 3])

    result // $ExpectType number[]
  })
  it('with array of objects - case 1', () => {
    const list1 = [{a: 1}, {a: 2}]
    const list2 = [{a: 2}, {a: 3}]
    const result = union(list1, list2)
    result // $ExpectType { a: number; }[]
  })
  it('with array of objects - case 2', () => {
    const list1 = [{a: 1, b: 1}, {a: 2}]
    const list2 = [{a: 2}, {a: 3, b: 3}]
    const result = union(list1, list2)
    result[0].a // $ExpectType number
    result[0].b // $ExpectType number | undefined
  })
})

describe('R.union - curried', () => {
  it('happy', () => {
    const result = union([1, 2])([2, 3])

    result // $ExpectType number[]
  })
  it('with array of objects - case 1', () => {
    const list1 = [{a: 1}, {a: 2}]
    const list2 = [{a: 2}, {a: 3}]
    const result = union(list1)(list2)
    result // $ExpectType { a: number; }[]
  })
  it('with array of objects - case 2', () => {
    const list1 = [{a: 1, b: 1}, {a: 2}]
    const list2 = [{a: 2}, {a: 3, b: 3}]
    const result = union(list1)(list2)
    result[0].a // $ExpectType number
    result[0].b // $ExpectType number | undefined
  })
})

uniq

uniq<T>(list: T[]): T[]

It returns a new array containing only one copy of each element of list.

R.equals is used to determine equality.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B1%2C%201%2C%20%7Ba%3A%201%7D%2C%20%7Ba%3A%202%7D%2C%20%7Ba%3A1%7D%5D%0A%0Aconst%20result%20%3D%20R.uniq(list)%0A%2F%2F%20%3D%3E%20%5B1%2C%20%7Ba%3A%201%7D%2C%20%7Ba%3A%202%7D%5D">Try this <strong>R.uniq</strong> example in Rambda REPL</a>

uniq<T>(list: T[]): T[];

import { _Set } from './_internals/set.js'

export function uniq(list){
  const set = new _Set()
  const willReturn = []
  list.forEach(item => {
    if (set.checkUniqueness(item)){
      willReturn.push(item)
    }
  })

  return willReturn
}

import { uniq } from './uniq.js'

test('happy', () => {
  const list = [ 1, 2, 3, 3, 3, 1, 2, 0 ]
  expect(uniq(list)).toEqual([ 1, 2, 3, 0 ])
})

test('with object', () => {
  const list = [ { a : 1 }, { a : 2 }, { a : 1 }, { a : 2 } ]
  expect(uniq(list)).toEqual([ { a : 1 }, { a : 2 } ])
})

test('with nested array', () => {
  expect(uniq([ [ 42 ], [ 42 ] ])).toEqual([ [ 42 ] ])
})

test('with booleans', () => {
  expect(uniq([ [ false ], [ false ], [ true ] ])).toEqual([ [ false ], [ true ] ])
})

test('with falsy values', () => {
  expect(uniq([ undefined, null ])).toEqual([ undefined, null ])
})

test('can distinct between string and number', () => {
  expect(uniq([ 1, '1' ])).toEqual([ 1, '1' ])
})

import {uniq} from 'rambda'

describe('R.uniq', () => {
  it('happy', () => {
    const result = uniq([1, 2, 3, 3, 3, 1, 2, 0])
    result // $ExpectType number[]
  })
})

uniqBy

It applies uniqueness to input list based on function that defines what to be used for comparison between elements.

R.equals is used to determine equality.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%7Ba%3A1%7D%2C%20%7Ba%3A2%7D%2C%20%7Ba%3A1%7D%5D%0Aconst%20result%20%3D%20R.uniqBy(x%20%3D%3E%20x%2C%20list)%0A%0A%2F%2F%20%3D%3E%20%5B%7Ba%3A1%7D%2C%20%7Ba%3A2%7D%5D">Try this <strong>R.uniqBy</strong> example in Rambda REPL</a>

uniqWith

uniqWith<T, U>(predicate: (x: T, y: T) => boolean, list: T[]): T[]

It returns a new array containing only one copy of each element in list according to predicate function.

This predicate should return true, if two elements are equal.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list%20%3D%20%5B%0A%20%20%7Bid%3A%200%2C%20title%3A'foo'%7D%2C%0A%20%20%7Bid%3A%201%2C%20title%3A'bar'%7D%2C%0A%20%20%7Bid%3A%202%2C%20title%3A'baz'%7D%2C%0A%20%20%7Bid%3A%203%2C%20title%3A'foo'%7D%2C%0A%20%20%7Bid%3A%204%2C%20title%3A'bar'%7D%2C%0A%5D%0A%0Aconst%20expected%20%3D%20%5B%0A%20%20%7Bid%3A%200%2C%20title%3A'foo'%7D%2C%0A%20%20%7Bid%3A%201%2C%20title%3A'bar'%7D%2C%0A%20%20%7Bid%3A%202%2C%20title%3A'baz'%7D%2C%0A%5D%0A%0Aconst%20predicate%20%3D%20(x%2Cy)%20%3D%3E%20x.title%20%3D%3D%3D%20y.title%0A%0Aconst%20result%20%3D%20R.uniqWith(predicate%2C%20list)%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.uniqWith</strong> example in Rambda REPL</a>

uniqWith<T, U>(predicate: (x: T, y: T) => boolean, list: T[]): T[];
uniqWith<T, U>(predicate: (x: T, y: T) => boolean): (list: T[]) => T[];

function includesWith(
  predicate, target, list
){
  let willReturn = false
  let index = -1

  while (++index < list.length && !willReturn){
    const value = list[ index ]

    if (predicate(target, value)){
      willReturn = true
    }
  }

  return willReturn
}

export function uniqWith(predicate, list){
  if (arguments.length === 1) return _list => uniqWith(predicate, _list)

  let index = -1
  const willReturn = []

  while (++index < list.length){
    const value = list[ index ]

    if (!includesWith(
      predicate, value, willReturn
    )){
      willReturn.push(value)
    }
  }

  return willReturn
}

import { uniqWith as uniqWithRamda } from 'ramda'

import { uniqWith } from './uniqWith.js'

const list = [ { a : 1 }, { a : 1 } ]

test('happy', () => {
  const fn = (x, y) => x.a === y.a

  const result = uniqWith(fn, list)
  expect(result).toEqual([ { a : 1 } ])
})

test('with list of strings', () => {
  const fn = (x, y) => x.length === y.length
  const list = [ '0', '11', '222', '33', '4', '55' ]
  const result = uniqWith(fn)(list)
  const resultRamda = uniqWithRamda(fn, list)
  expect(result).toEqual([ '0', '11', '222' ])
  expect(resultRamda).toEqual([ '0', '11', '222' ])
})

import {uniqWith} from 'rambda'

describe('R.uniqWith', () => {
  it('happy', () => {
    const list = [{a: 1}, {a: 1}]

    const fn = (x: any, y: any) => x.a === y.a

    const result = uniqWith(fn, list)
    result // $ExpectType { a: number; }[]
  })
})

unless

unless<T, U>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U, x: T): T | U

The method returns function that will be called with argument input.

If predicate(input) returns false, then the end result will be the outcome of whenFalse(input).

In the other case, the final output will be the input itself.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20fn%20%3D%20R.unless(%0A%20%20x%20%3D%3E%20x%20%3E%202%2C%0A%20%20x%20%3D%3E%20x%20%2B%2010%0A)%0A%0Aconst%20result%20%3D%20%5B%0A%20%20fn(1)%2C%0A%20%20fn(5)%0A%5D%0A%2F%2F%20%3D%3E%20%5B11%2C%205%5D">Try this <strong>R.unless</strong> example in Rambda REPL</a>

unless<T, U>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U, x: T): T | U;
unless<T, U>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => U): (x: T) => T | U;
unless<T>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => T, x: T): T;
unless<T>(predicate: (x: T) => boolean, whenFalseFn: (x: T) => T): (x: T) => T;

import { curry } from './curry.js'

function unlessFn(
  predicate, whenFalseFn, input
){
  if (predicate(input)) return input

  return whenFalseFn(input)
}

export const unless = curry(unlessFn)

import { inc } from './inc.js'
import { isNil } from './isNil.js'
import { unless } from './unless.js'

test('happy', () => {
  const safeInc = unless(isNil, inc)
  expect(safeInc(null)).toBeNull()
  expect(safeInc(1)).toBe(2)
})

test('curried', () => {
  const safeIncCurried = unless(isNil)(inc)
  expect(safeIncCurried(null)).toBeNull()
})

test('with 3 inputs', () => {
  let result = unless(x => x.startsWith('/'), x=> x.concat('/'), '/api')
  expect(result).toBe('/api')
})

import {unless, inc} from 'rambda'

describe('R.unless', () => {
  it('happy', () => {
    const fn = unless(x => x > 5, inc)
    const result = fn(1)
    result // $ExpectType number
  })
  it('with one explicit type', () => {
    const result = unless(
      x => {
        x // $ExpectType number
        return x > 5
      },
      x => {
        x // $ExpectType number
        return x + 1
      },
      1
    )
    result // $ExpectType number
  })
  it('with two different explicit types', () => {
    const result = unless(
      x => {
        x // $ExpectType number
        return x > 5
      },
      x => {
        x // $ExpectType number
        return `${x}-foo`
      },
      1
    )
    result // $ExpectType string | number
  })
})

describe('R.unless - curried', () => {
  it('happy', () => {
    const fn = unless(x => x > 5, inc)
    const result = fn(1)
    result // $ExpectType number
  })
  it('with one explicit type', () => {
    const fn = unless<number>(
      x => {
        x // $ExpectType number
        return x > 5
      },
      x => {
        x // $ExpectType number
        return x + 1
      }
    )
    const result = fn(1)
    result // $ExpectType number
  })
  it('with two different explicit types', () => {
    const fn = unless<number, string>(
      x => {
        x // $ExpectType number
        return x > 5
      },
      x => {
        x // $ExpectType number
        return `${x}-foo`
      }
    )
    const result = fn(1)
    result // $ExpectType string | number
  })
})

unnest

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20R.unnest(%5B1%2C%20%5B2%5D%2C%20%5B%5B3%5D%5D%5D)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%2C%20%5B3%5D%5D">Try this <strong>R.unnest</strong> example in Rambda REPL</a>

unwind

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7B%0A%20%20a%3A%201%2C%0A%20%20b%3A%20%5B2%2C%203%5D%2C%0A%7D%0Aconst%20result%20%3D%20R.unwind('b'%2C%20obj)%0Aconst%20expected%20%3D%20%5B%7Ba%3A1%2C%20b%3A2%7D%2C%20%7Ba%3A1%2C%20b%3A3%7D%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.unwind</strong> example in Rambda REPL</a>

update

update<T>(index: number, newValue: T, list: T[]): T[]

It returns a copy of list with updated element at index with newValue.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20index%20%3D%202%0Aconst%20newValue%20%3D%2088%0Aconst%20list%20%3D%20%5B1%2C%202%2C%203%2C%204%2C%205%5D%0A%0Aconst%20result%20%3D%20R.update(index%2C%20newValue%2C%20list)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%2C%2088%2C%204%2C%205%5D">Try this <strong>R.update</strong> example in Rambda REPL</a>

update<T>(index: number, newValue: T, list: T[]): T[];
update<T>(index: number, newValue: T): (list: T[]) => T[];

import { cloneList } from './_internals/cloneList.js'
import { curry } from './curry.js'

export function updateFn(
  index, newValue, list
){
  const clone = cloneList(list)
  if (index === -1) return clone.fill(newValue, index)

  return clone.fill(
    newValue, index, index + 1
  )
}

export const update = curry(updateFn)

import { update } from './update.js'

const list = [ 1, 2, 3 ]

test('happy', () => {
  const newValue = 8
  const index = 1
  const result = update(
    index, newValue, list
  )
  const curriedResult = update(index, newValue)(list)
  const tripleCurriedResult = update(index)(newValue)(list)

  const expected = [ 1, 8, 3 ]
  expect(result).toEqual(expected)
  expect(curriedResult).toEqual(expected)
  expect(tripleCurriedResult).toEqual(expected)
})

test('list has no such index', () => {
  const newValue = 8
  const index = 10
  const result = update(
    index, newValue, list
  )

  expect(result).toEqual(list)
})

test('with negative index', () => {
  expect(update(
    -1, 10, [ 1 ]
  )).toEqual([ 10 ])
  expect(update(
    -1, 10, []
  )).toEqual([])
  expect(update(
    -1, 10, list
  )).toEqual([ 1, 2, 10 ])
  expect(update(
    -2, 10, list
  )).toEqual([ 1, 10, 3 ])
  expect(update(
    -3, 10, list
  )).toEqual([ 10, 2, 3 ])
})

import {update} from 'rambda'

describe('R.update', () => {
  it('happy', () => {
    const result = update(1, 0, [1, 2, 3])
    result // $ExpectType number[]
  })
})

values

values<T extends object, K extends keyof T>(obj: T): T[K][]

With correct input, this is nothing more than Object.values(Record<string, unknown>). If obj is not an object, then it returns an empty array.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20obj%20%3D%20%7Ba%3A1%2C%20b%3A2%7D%0A%0Aconst%20result%20%3D%20R.values(Record%3Cstring%2C%20unknown%3E)%0A%2F%2F%20%3D%3E%20%5B1%2C%202%5D">Try this <strong>R.values</strong> example in Rambda REPL</a>

values<T extends object, K extends keyof T>(obj: T): T[K][];

import { type } from './type.js'

export function values(obj){
  if (type(obj) !== 'Object') return []
  return Object.values(obj)
}

import { values } from './values.js'

test('happy', () => {
  expect(values({
    a : 1,
    b : 2,
    c : 3,
  })).toEqual([ 1, 2, 3 ])
})

test('with bad input', () => {
  expect(values(null)).toEqual([])
  expect(values(undefined)).toEqual([])
  expect(values(55)).toEqual([])
  expect(values('foo')).toEqual([])
  expect(values(true)).toEqual([])
  expect(values(false)).toEqual([])
  expect(values(NaN)).toEqual([])
  expect(values(Infinity)).toEqual([])
  expect(values([])).toEqual([])
})

import {values} from 'rambda'

describe('R.values', () => {
  it('happy', () => {
    const result = values({
      a: 1,
      b: 2,
      c: 3,
    })
    result // $ExpectType number[]
  })
})

view

view<S, A>(lens: Lens<S, A>): (obj: S) => A

It returns the value of lens focus over target object.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20lens%20%3D%20R.lensProp('x')%0A%0AR.view(lens%2C%20%7Bx%3A%201%2C%20y%3A%202%7D)%20%2F%2F%20%3D%3E%201%0Aconst%20result%20%3D%20R.view(lens%2C%20%7Bx%3A%204%2C%20y%3A%202%7D)%20%2F%2F%20%3D%3E%204">Try this <strong>R.view</strong> example in Rambda REPL</a>

view<S, A>(lens: Lens<S, A>): (obj: S) => A;
view<S, A>(lens: Lens<S, A>, obj: S): A;

const Const = x => ({
  x,
  map : fn => Const(x),
})

export function view(lens, target){
  if (arguments.length === 1) return _target => view(lens, _target)

  return lens(Const)(target).x
}

import { assoc } from './assoc.js'
import { lens } from './lens.js'
import { prop } from './prop.js'
import { view } from './view.js'

const testObject = { foo : 'Led Zeppelin' }
const assocLens = lens(prop('foo'), assoc('foo'))

test('happy', () => {
  expect(view(assocLens, testObject)).toBe('Led Zeppelin')
})

when

when<T, U>(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U, input: T): T | U

It pass input to predicate function and if the result is true, it will return the result of whenTrueFn(input). If the predicate returns false, then it will simply return input.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20predicate%20%3D%20x%20%3D%3E%20typeof%20x%20%3D%3D%3D%20'number'%0Aconst%20whenTrueFn%20%3D%20R.add(11)%0A%0Aconst%20fn%20%3D%20when(predicate%2C%20whenTrueResult)%0A%0Aconst%20positiveInput%20%3D%2088%0Aconst%20negativeInput%20%3D%20'foo'%0A%0Aconst%20result%20%3D%20%5B%0A%20%20fn(positiveInput)%2C%0A%20%20fn(positiveInput)%2C%0A%5D%0A%0Aconst%20expected%20%3D%20%5B%0A%20%2099%2C%0A%20%20'foo'%2C%0A%5D%0A%2F%2F%20%3D%3E%20%60result%60%20is%20equal%20to%20%60expected%60">Try this <strong>R.when</strong> example in Rambda REPL</a>

when<T, U>(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U, input: T): T | U;
when<T, U>(predicate: (x: T) => boolean, whenTrueFn: (a: T) => U): (input: T) => T | U;
when<T, U>(predicate: (x: T) => boolean): ((whenTrueFn: (a: T) => U) => (input: T) => T | U);

import { curry } from './curry.js'

function whenFn(
  predicate, whenTrueFn, input
){
  if (!predicate(input)) return input

  return whenTrueFn(input)
}

export const when = curry(whenFn)

import { add } from './add.js'
import { when } from './when.js'

const predicate = x => typeof x === 'number'

test('happy', () => {
  const fn = when(predicate, add(11))
  expect(fn(11)).toBe(22)
  expect(fn('foo')).toBe('foo')
})

import {when} from 'rambda'

const predicate = (x: number) => x > 2
const whenTrueFn = (x: number) => String(x)

describe('R.when', () => {
  it('happy', () => {
    const result = when(predicate, whenTrueFn, 1)
    result // $ExpectType string | 1
  })

  it('curry 1', () => {
    const fn = when(predicate, whenTrueFn)
    const result = fn(1)
    result // $ExpectType string | number
  })

  it('curry 2 require explicit types', () => {
    const fn = when<number, string>(predicate)(whenTrueFn)
    const result = fn(1)
    result // $ExpectType string | number
  })
})

where

where<T, U>(conditions: T, input: U): boolean

It returns true if all each property in conditions returns true when applied to corresponding property in input object.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20condition%20%3D%20R.where(%7B%0A%20%20a%20%3A%20x%20%3D%3E%20typeof%20x%20%3D%3D%3D%20%22string%22%2C%0A%20%20b%20%3A%20x%20%3D%3E%20x%20%3D%3D%3D%204%0A%7D)%0Aconst%20input%20%3D%20%7B%0A%20%20a%20%3A%20%22foo%22%2C%0A%20%20b%20%3A%204%2C%0A%20%20c%20%3A%2011%2C%0A%7D%0A%0Aconst%20result%20%3D%20condition(input)%20%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.where</strong> example in Rambda REPL</a>

where<T, U>(conditions: T, input: U): boolean;
where<T>(conditions: T): <U>(input: U) => boolean;
where<ObjFunc2, U>(conditions: ObjFunc2, input: U): boolean;
where<ObjFunc2>(conditions: ObjFunc2): <U>(input: U) => boolean;

export function where(conditions, input){
  if (input === undefined){
    return _input => where(conditions, _input)
  }
  let flag = true
  for (const prop in conditions){
    if (!flag) continue
    const result = conditions[ prop ](input[ prop ])
    if (flag && result === false){
      flag = false
    }
  }

  return flag
}

import { equals } from './equals.js'
import { where } from './where.js'

test('when true', () => {
  const result = where({
    a : equals('foo'),
    b : equals('bar'),
  },
  {
    a : 'foo',
    b : 'bar',
    x : 11,
    y : 19,
  })

  expect(result).toBeTrue()
})

test('when false | early exit', () => {
  let counter = 0
  const equalsFn = expected => input => {
    console.log(expected, 'expected')
    counter++

    return input === expected
  }
  const predicate = where({
    a : equalsFn('foo'),
    b : equalsFn('baz'),
  })
  expect(predicate({
    a : 'notfoo',
    b : 'notbar',
  })).toBeFalse()
  expect(counter).toBe(1)
})

import {where, equals} from 'rambda'

describe('R.where', () => {
  it('happy', () => {
    const input = {
      a: 'foo',
      b: 'bar',
      x: 11,
      y: 19,
    }
    const conditions = {
      a: equals('foo'),
      b: equals('bar'),
    }
    const result = where(conditions, input)
    const curriedResult = where(conditions)(input)
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
})

whereAny

Same as R.where, but it will return true if at least one condition check returns true.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20conditions%20%3D%20%7B%0A%20%20a%3A%20a%20%3D%3E%20a%20%3E%201%2C%0A%20%20b%3A%20b%20%3D%3E%20b%20%3E%202%2C%0A%7D%0Aconst%20result%20%3D%20%5B%0A%20%20R.whereAny(conditions%2C%20%7Bb%3A3%7D)%2C%0A%20%20R.whereAny(conditions%2C%20%7Bc%3A4%7D)%0A%5D%0A%2F%2F%20%3D%3E%20%5Btrue%2C%20false%5D">Try this <strong>R.whereAny</strong> example in Rambda REPL</a>

whereEq

whereEq<T, U>(condition: T, input: U): boolean

It will return true if all of input object fully or partially include rule object.

R.equals is used to determine equality.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20condition%20%3D%20%7B%20a%20%3A%20%7B%20b%20%3A%201%20%7D%20%7D%0Aconst%20input%20%3D%20%7B%0A%20%20a%20%3A%20%7B%20b%20%3A%201%20%7D%2C%0A%20%20c%20%3A%202%0A%7D%0A%0Aconst%20result%20%3D%20whereEq(condition%2C%20input)%0A%2F%2F%20%3D%3E%20true">Try this <strong>R.whereEq</strong> example in Rambda REPL</a>

whereEq<T, U>(condition: T, input: U): boolean;
whereEq<T>(condition: T): <U>(input: U) => boolean;

import { equals } from './equals.js'
import { filter } from './filter.js'

export function whereEq(condition, input){
  if (arguments.length === 1){
    return _input => whereEq(condition, _input)
  }

  const result = filter((conditionValue, conditionProp) =>
    equals(conditionValue, input[ conditionProp ]),
  condition)

  return Object.keys(result).length === Object.keys(condition).length
}

import { whereEq } from './whereEq.js'

test('when true', () => {
  const condition = { a : 1 }
  const input = {
    a : 1,
    b : 2,
  }

  const result = whereEq(condition, input)
  const expectedResult = true

  expect(result).toEqual(expectedResult)
})

test('when false', () => {
  const condition = { a : 1 }
  const input = { b : 2 }

  const result = whereEq(condition, input)
  const expectedResult = false

  expect(result).toEqual(expectedResult)
})

test('with nested object', () => {
  const condition = { a : { b : 1 } }
  const input = {
    a : { b : 1 },
    c : 2,
  }

  const result = whereEq(condition)(input)
  const expectedResult = true

  expect(result).toEqual(expectedResult)
})

test('with wrong input', () => {
  const condition = { a : { b : 1 } }

  expect(() => whereEq(condition, null)).toThrowErrorMatchingInlineSnapshot('"Cannot read properties of null (reading \'a\')"')
})

import {whereEq} from 'rambda'

describe('R.whereEq', () => {
  it('happy', () => {
    const result = whereEq({a: {b: 2}}, {b: 2})
    const curriedResult = whereEq({a: {b: 2}})({b: 2})
    result // $ExpectType boolean
    curriedResult // $ExpectType boolean
  })
})

without

without<T>(matchAgainst: T[], source: T[]): T[]

It will return a new array, based on all members of source list that are not part of matchAgainst list.

R.equals is used to determine equality.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20source%20%3D%20%5B1%2C%202%2C%203%2C%204%5D%0Aconst%20matchAgainst%20%3D%20%5B2%2C%203%5D%0A%0Aconst%20result%20%3D%20R.without(matchAgainst%2C%20source)%0A%2F%2F%20%3D%3E%20%5B1%2C%204%5D">Try this <strong>R.without</strong> example in Rambda REPL</a>

without<T>(matchAgainst: T[], source: T[]): T[];
without<T>(matchAgainst: T[]): (source: T[]) => T[];

import { _indexOf } from './equals.js'
import { reduce } from './reduce.js'

export function without(matchAgainst, source){
  if (source === undefined){
    return _source => without(matchAgainst, _source)
  }

  return reduce(
    (prev, current) =>
      _indexOf(current, matchAgainst) > -1 ? prev : prev.concat(current),
    [],
    source
  )
}

import { without as withoutRamda } from 'ramda'

import { without } from './without.js'

test('should return a new list without values in the first argument', () => {
  const itemsToOmit = [ 'A', 'B', 'C' ]
  const collection = [ 'A', 'B', 'C', 'D', 'E', 'F' ]

  expect(without(itemsToOmit, collection)).toEqual([ 'D', 'E', 'F' ])
  expect(without(itemsToOmit)(collection)).toEqual([ 'D', 'E', 'F' ])
})

test('with list of objects', () => {
  const itemsToOmit = [ { a : 1 }, { c : 3 } ]
  const collection = [ { a : 1 }, { b : 2 }, { c : 3 }, { d : 4 } ]
  const expected = [ { b : 2 }, { d : 4 } ]

  expect(without(itemsToOmit, collection)).toEqual(expected)
  expect(withoutRamda(itemsToOmit, collection)).toEqual(expected)
})

test('ramda accepts string as target input while rambda throws', () => {
  expect(withoutRamda('0:1', [ '0', '0:1' ])).toEqual([ '0:1' ])
  expect(() =>
    without('0:1', [ '0', '0:1' ])).toThrowErrorMatchingInlineSnapshot('"Cannot read property \'indexOf\' of 0:1"')
  expect(without([ '0:1' ], [ '0', '0:1' ])).toEqual([ '0' ])
})

test('ramda test', () => {
  expect(without([ 1, 2 ])([ 1, 2, 1, 3, 4 ])).toEqual([ 3, 4 ])
})

import {without} from 'rambda'

const itemsToOmit = ['A', 'B', 'C']
const collection = ['A', 'B', 'C', 'D', 'E', 'F']

describe('R.without', () => {
  it('happy', () => {
    const result = without(itemsToOmit, collection)

    result // $ExpectType string[]
  })
  it('curried', () => {
    const result = without(itemsToOmit)(collection)

    result // $ExpectType string[]
  })
})

xor

xor(x: boolean, y: boolean): boolean

Logical XOR

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20result%20%3D%20%5B%0A%20%20xor(true%2C%20true)%2C%0A%20%20xor(false%2C%20false)%2C%0A%20%20xor(false%2C%20true)%2C%0A%5D%0A%2F%2F%20%3D%3E%20%5Bfalse%2C%20false%2C%20true%5D">Try this <strong>R.xor</strong> example in Rambda REPL</a>

xor(x: boolean, y: boolean): boolean;
xor(y: boolean): (y: boolean) => boolean;

export function xor(a, b){
  if (arguments.length === 1) return _b => xor(a, _b)

  return Boolean(a) && !b || Boolean(b) && !a
}

import { xor } from './xor.js'

test('compares two values with exclusive or', () => {
  expect(xor(true, true)).toBeFalse()
  expect(xor(true, false)).toBeTrue()
  expect(xor(false, true)).toBeTrue()
  expect(xor(false, false)).toBeFalse()
})

test('when both values are truthy, it should return false', () => {
  expect(xor(true, 'foo')).toBeFalse()
  expect(xor(42, true)).toBeFalse()
  expect(xor('foo', 42)).toBeFalse()
  expect(xor({}, true)).toBeFalse()
  expect(xor(true, [])).toBeFalse()
  expect(xor([], {})).toBeFalse()
  expect(xor(new Date(), true)).toBeFalse()
  expect(xor(true, Infinity)).toBeFalse()
  expect(xor(Infinity, new Date())).toBeFalse()
})

test('when both values are falsy, it should return false', () => {
  expect(xor(null, false)).toBeFalse()
  expect(xor(false, undefined)).toBeFalse()
  expect(xor(undefined, null)).toBeFalse()
  expect(xor(0, false)).toBeFalse()
  expect(xor(false, NaN)).toBeFalse()
  expect(xor(NaN, 0)).toBeFalse()
  expect(xor('', false)).toBeFalse()
})

test('when one argument is truthy and the other is falsy, it should return true', () => {
  expect(xor('foo', null)).toBeTrue()
  expect(xor(null, 'foo')).toBeTrue()
  expect(xor(undefined, 42)).toBeTrue()
  expect(xor(42, undefined)).toBeTrue()
  expect(xor(Infinity, NaN)).toBeTrue()
  expect(xor(NaN, Infinity)).toBeTrue()
  expect(xor({}, '')).toBeTrue()
  expect(xor('', {})).toBeTrue()
  expect(xor(new Date(), 0)).toBeTrue()
  expect(xor(0, new Date())).toBeTrue()
  expect(xor([], null)).toBeTrue()
  expect(xor(undefined, [])).toBeTrue()
})

import {xor} from 'rambda'

describe('R.xor', () => {
  it('happy', () => {
    xor(true, false) // $ExpectType boolean
  })
  it('curry', () => {
    xor(true)(false) // $ExpectType boolean
  })
})

zip

zip<K, V>(x: K[], y: V[]): KeyValuePair<K, V>[]

It will return a new array containing tuples of equally positions items from both x and y lists.

The returned list will be truncated to match the length of the shortest supplied list.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20x%20%3D%20%5B1%2C%202%5D%0Aconst%20y%20%3D%20%5B'A'%2C%20'B'%5D%0AR.zip(x%2C%20y)%0A%2F%2F%20%3D%3E%20%5B%5B1%2C%20'A'%5D%2C%20%5B2%2C%20'B'%5D%5D%0A%0A%2F%2F%20truncates%20to%20shortest%20list%0Aconst%20result%20%3D%20R.zip(%5B...x%2C%203%5D%2C%20%5B'A'%2C%20'B'%5D)%0A%2F%2F%20%3D%3E%20%5B%5B1%2C%20'A'%5D%2C%20%5B2%2C%20'B'%5D%5D">Try this <strong>R.zip</strong> example in Rambda REPL</a>

zip<K, V>(x: K[], y: V[]): KeyValuePair<K, V>[];
zip<K>(x: K[]): <V>(y: V[]) => KeyValuePair<K, V>[];

export function zip(left, right){
  if (arguments.length === 1) return _right => zip(left, _right)

  const result = []
  const length = Math.min(left.length, right.length)

  for (let i = 0; i < length; i++){
    result[ i ] = [ left[ i ], right[ i ] ]
  }

  return result
}

import { zip } from './zip.js'

const array1 = [ 1, 2, 3 ]
const array2 = [ 'A', 'B', 'C' ]

test('should return an array', () => {
  const actual = zip(array1)(array2)
  expect(actual).toBeInstanceOf(Array)
})

test('should return and array or tuples', () => {
  const expected = [
    [ 1, 'A' ],
    [ 2, 'B' ],
    [ 3, 'C' ],
  ]
  const actual = zip(array1, array2)
  expect(actual).toEqual(expected)
})

test('should truncate result to length of shorted input list', () => {
  const expectedA = [
    [ 1, 'A' ],
    [ 2, 'B' ],
  ]
  const actualA = zip([ 1, 2 ], array2)
  expect(actualA).toEqual(expectedA)

  const expectedB = [
    [ 1, 'A' ],
    [ 2, 'B' ],
  ]
  const actualB = zip(array1, [ 'A', 'B' ])
  expect(actualB).toEqual(expectedB)
})

import {zip} from 'rambda'

describe('R.zip', () => {
  it('happy', () => {
    const array1 = [1, 2, 3]
    const array2 = ['A', 'B', 'C']

    const result = zip(array1)(array2)
    result // $ExpectType KeyValuePair<number, string>[]
  })
})

zipObj

zipObj<T, K extends string>(keys: K[], values: T[]): { [P in K]: T }

It will return a new object with keys of keys array and values of values array.

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20keys%20%3D%20%5B'a'%2C%20'b'%2C%20'c'%5D%0A%0AR.zipObj(keys%2C%20%5B1%2C%202%2C%203%5D)%0A%2F%2F%20%3D%3E%20%7Ba%3A%201%2C%20b%3A%202%2C%20c%3A%203%7D%0A%0A%2F%2F%20truncates%20to%20shortest%20list%0Aconst%20result%20%3D%20R.zipObj(keys%2C%20%5B1%2C%202%5D)%0A%2F%2F%20%3D%3E%20%7Ba%3A%201%2C%20b%3A%202%7D">Try this <strong>R.zipObj</strong> example in Rambda REPL</a>

zipObj<T, K extends string>(keys: K[], values: T[]): { [P in K]: T };
zipObj<K extends string>(keys: K[]): <T>(values: T[]) => { [P in K]: T };
zipObj<T, K extends number>(keys: K[], values: T[]): { [P in K]: T };
zipObj<K extends number>(keys: K[]): <T>(values: T[]) => { [P in K]: T };

import { take } from './take.js'

export function zipObj(keys, values){
  if (arguments.length === 1) return yHolder => zipObj(keys, yHolder)

  return take(values.length, keys).reduce((
    prev, xInstance, i
  ) => {
    prev[ xInstance ] = values[ i ]

    return prev
  }, {})
}

import { equals } from './equals.js'
import { zipObj } from './zipObj.js'

test('zipObj', () => {
  expect(zipObj([ 'a', 'b', 'c' ], [ 1, 2, 3 ])).toEqual({
    a : 1,
    b : 2,
    c : 3,
  })
})

test('0', () => {
  expect(zipObj([ 'a', 'b' ])([ 1, 2, 3 ])).toEqual({
    a : 1,
    b : 2,
  })
})

test('1', () => {
  expect(zipObj([ 'a', 'b', 'c' ])([ 1, 2 ])).toEqual({
    a : 1,
    b : 2,
  })
})

test('ignore extra keys', () => {
  const result = zipObj([ 'a', 'b', 'c', 'd', 'e', 'f' ], [ 1, 2, 3 ])
  const expected = {
    a : 1,
    b : 2,
    c : 3,
  }

  expect(equals(result, expected)).toBeTrue()
})

import {zipObj} from 'rambda'

describe('R.zipObj', () => {
  it('happy', () => {
    // this is wrong since 24.10.2020 `@types/ramda` changes
    const result = zipObj(['a', 'b', 'c', 'd'], [1, 2, 3])
    ;[result.a, result.b, result.c, result.d] // $ExpectType number[]
  })
  it('imported from @types/ramda', () => {
    const result = zipObj(['a', 'b', 'c'], [1, 2, 3])
    const curriedResult = zipObj(['a', 'b', 'c'])([1, 2, 3])
    ;[result.a, result.b, result.c] // $ExpectType number[]
    ;[curriedResult.a, curriedResult.b, curriedResult.c] // $ExpectType number[]
  })
})

zipWith

zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult, list1: T[], list2: U[]): TResult[]

<a title="redirect to Rambda Repl site" href="https://rambda.now.sh?const%20list1%20%3D%20%5B%2010%2C%2020%2C%2030%2C%2040%20%5D%0Aconst%20list2%20%3D%20%5B%20100%2C%20200%20%5D%0A%0Aconst%20result%20%3D%20R.zipWith(%0A%20%20R.add%2C%20list1%2C%20list2%0A)%0A%2F%2F%20%3D%3E%20%5B110%2C%20220%5D">Try this <strong>R.zipWith</strong> example in Rambda REPL</a>

zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult, list1: T[], list2: U[]): TResult[];
zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult, list1: T[]): (list2: U[]) => TResult[];
zipWith<T, U, TResult>(fn: (x: T, y: U) => TResult): (list1: T[], list2: U[]) => TResult[];

import { curry } from './curry.js'
import { take } from './take.js'

function zipWithFn(
  fn, x, y
){
  return take(x.length > y.length ? y.length : x.length, x).map((xInstance, i) => fn(xInstance, y[ i ]))
}

export const zipWith = curry(zipWithFn)

import { add } from './add.js'
import { zipWith } from './zipWith.js'

const list1 = [ 1, 2, 3 ]
const list2 = [ 10, 20, 30, 40 ]
const list3 = [ 100, 200 ]

test('when second list is shorter', () => {
  const result = zipWith(
    add, list1, list3
  )
  expect(result).toEqual([ 101, 202 ])
})

test('when second list is longer', () => {
  const result = zipWith(
    add, list1, list2
  )
  expect(result).toEqual([ 11, 22, 33 ])
})

import {zipWith} from 'rambda'

const list1 = [1, 2]
const list2 = [10, 20, 30]

describe('R.zipWith', () => {
  it('happy', () => {
    const result = zipWith(
      (x, y) => {
        x // $ExpectType number
        y // $ExpectType number
        return `${x}-${y}`
      },
      list1,
      list2
    )

    result // $ExpectType string[]
  })
  it('curried', () => {
    const result = zipWith((x, y) => {
      x // $ExpectType unknown
      y // $ExpectType unknown
      return `${x}-${y}`
    })(list1, list2)

    result // $ExpectType string[]
  })
})

❯ CHANGELOG

9.4.2

• Fix bug with R.differenceWith when two arrays has same length - Issue #750

9.4.1

• Allow path input to not be transformed when string numbers are there - Issue #750

9.4.0

• Fix deno release

• Fix too strict true condition in R.ifElse - Issue #750

• Change R.groupBy typings to match @types/ramda typings

9.3.0

• Breaking change in relation to TS typings of R.assoc, R.dissoc and R.modify - https://github.com/ramda/types/pull/37

• Add R.isNotEmpty as it is new method in Ramda

• Fix R.head/R.last TS definition - It returns undefined if array has length of 0. Before

9.2.1

• Broken Deno build - Issue #731

9.2.0

• R.once TS type definition miss to context argument and its type - Issue #728

• Fix implementation of R.unless function - https://github.com/selfrefactor/rambda/pull/726

9.1.1

• Faster R.equals with Object.is short circuit - https://github.com/selfrefactor/rambda/pull/725

• Fix R.cond transform is unary - https://github.com/selfrefactor/rambda/issues/720

9.1.0

Add these methods

• insert
• insertAll
• lt
• lte
• isNotNil
• pickBy
• pathSatisfies
• swap
• mergeDeepLeft

9.0.1

• Fix bad TS typings, due to missing declaration - Issue #716

9.0.0

Breaking change in TS definitions of lenses as now they are synced to Ramda types.

• Add R.sortWith - Issue #707

• Add R.innerJoin, R.gt, R.gte, R.reduceBy, R.hasIn

8.6.0

• Wrong typing for R.dissocPath - Issue #709

• Update build dependencies

8.5.0

• Revert changes in R.anyPass introduced in 8.4.0 release. The reason is that the change was breaking the library older than 5.2.0 TypeScript.

• Wrong R.partial TS definition - Issue #705

• Add R.dropRepeatsBy

• Add R.empty

• Add R.eqBy

• Add R.forEachObjIndexed

8.4.0

• Add R.dissocPath

• Fix TS definitions of R.head/R.last and add missing handle of empty string

• Add R.removeIndex - method was before only in Rambdax, but now since R.dissocPath is using it, it is added to main library.

• Allow R.omit to pass numbers as part of properties to omit, i.e. R.omit(['a', 1], {a: {1: 1, 2: 2}})

• R.keys always returns strings - MR #700

• Improve R.prepend/R.append type interference - MR #699

• Change R.reduce TS definitions so index is always received - MR #696

• Functions as a type guard in R.anyPass TS definitions - MR #695

• Fix R.append's curried type - MR #694

• Fix cannot compare errors in Deno with R.equals - Issue #704.

• Fix cannot compare BigInt with R.equals

8.3.0

Add the following methods:

• binary
• call
• collectBy
• comparator
• composeWith

8.2.0

Add the following methods:

• addIndex
• addIndexRight
• ap
• aperture
• applyTo
• ascend
• descend

8.1.0

• Fix input order of TS definitions for R.propEq method - Issue #688. The issue was due to 8.0.0 was shipped with TS definitions of 7.5.0 release.

• Add R.differenceWith method - Issue #91

8.0.0

• handle falsy values in merge methods - https://github.com/ramda/ramda/pull/3222

• R.head/R.last don't return undefined for non-empty arrays

• R.type supports dates in TS definition - Rambda already did support dates in JS.

• Improve typings of R.endsWith/startsWith with regard to string input. - PR #622

• Handle list as falsy value in R.reduce - Ramda MR

• R.nop is removed - it will be moved to Rambdax as R.noop

• R.includes is no longer using string literal in TypeScript definitions

Reason for breaking change - synchronize with Ramda 0.29.0 release:

• change order of R.propEq - Ramda MR

7.5.0

• IMPORTANT: Remove export property in package.json in order to allow Rambda support for projects with "type": "module" in package.json - Issue #667

• Add R.unnest - Rambdax issue 89

• R.uniq is not using R.equals as Ramda does - Issue #88

• Fix R.path(['non','existing','path'], obj) TS definition as 7.4.0 release caused TS errors - Issue #668

7.4.0

• Synchronize with @types/ramda - R.prop, R.path, R.pickAll

• Remove esm Rollup output due to tree-shaking issues.

• Upgrade all dev dependencies.

7.3.0

• Important - changing import declaration in package.json in order to fix tree-shaking issue - Issue #647

• Add R.modify

• Allow multiple inputs in TypeScript versions of R.anyPass and R.allPass - Issue #642

• Using wrong clone of object in R.mergeDeepRight - Issue #650

• Missing early return in R.where - Issue #648

• R.allPass doesn't accept more than 1 parameters for function predicates- Issue #604

7.2.1

• Remove bad typings of R.propIs which caused the library to cannot be build with TypeScript.

• Drop support for Wallaby as per https://github.com/wallabyjs/public/issues/3037

7.2.0

• Wrong R.update if index is -1 - PR #593

• Wrong curried typings in R.anyPass - Issue #642

• R.modifyPath not exported - Issue #640

• Add new method R.uniqBy. Implementation is coming from Ramda MR#2641

• Apply the following changes from @types/rambda:

-- [https://github.com/DefinitelyTyped/DefinitelyTyped/commit/bab47272d52fc7bb81e85da36dbe9c905a04d067](add AnyFunction and AnyConstructor)

-- Improve R.ifElse typings - https://github.com/DefinitelyTyped/DefinitelyTyped/pull/59291

-- Make R.propEq safe for null/undefined arguments - https://github.com/ramda/ramda/pull/2594/files

7.1.4

• R.mergeRight not found on Deno import - Issue #633

7.1.0

• Add R.mergeRight - introduced by Ramda's latest release. While Ramda renames R.merge, Rambda will keep R.merge.

• Rambda's pipe/compose doesn't return proper length of composed function which leads to issue with R.applySpec. It was fixed by using Ramda's pipe/compose logic - Issue #627

• Replace Async with Promise as return type of R.type.

• Add new types as TypeScript output for R.type - "Map", "WeakMap", "Generator", "GeneratorFunction", "BigInt", "ArrayBuffer"

• Add R.juxt method

• Add R.propSatisfies method

• Add new methods after Ramda version upgrade to 0.28.0:

-- R.count -- R.modifyPath -- R.on -- R.whereAny -- R.partialObject

7.0.3

Rambda.none has wrong logic introduced in version 7.0.0 - Issue #625

7.0.2

Rambda doesn't work with pnpm due to wrong export configuration - Issue #619

7.0.1

• Wrong ESM export configuration in package.json - Issue #614

7.0.0

• Breaking change - sync R.compose/R.pipe with @types/ramda. That is significant change so as safeguard, it will lead a major bump. Important - this lead to raising required TypeScript version to 4.2.2. In other words, to use Rambda you'll need TypeScript version 4.2.2 or newer.

Related commit in @types/ramda - https://github.com/DefinitelyTyped/DefinitelyTyped/commit/286eff4f76d41eb8f091e7437eabd8a60d97fc1f#diff-4f74803fa83a81e47cb17a7d8a4e46a7e451f4d9e5ce2f1bd7a70a72d91f4bc1

There are several other changes in @types/ramda as stated in this comment. This leads to change of typings for the following methods in Rambda:

-- R.unless

-- R.toString

-- R.ifElse

-- R.always

-- R.complement

-- R.cond

-- R.is

-- R.sortBy

-- R.dissoc

-- R.toPairs

-- R.assoc

-- R.toLower

-- R.toUpper

• One more reason for the breaking change is changing of export declarations in package.json based on this blog post and this merged Ramda's PR. This also led to renaming of babel.config.js to babel.config.cjs.

• Add R.apply, R.bind and R.unapply

• R.startsWith/R.endsWith now support lists as inputs. This way, it matches current Ramda behavior.

• Remove unused typing for R.chain.

• R.map/R.filter no longer accept bad inputs as iterable. This way, Rambda behaves more like Ramda, which also throws.

• Make R.lastIndexOf follow the logic of R.indexOf.

• Change R.type logic to Ramda logic. This way, R.type can return Error and Set as results.

• Add missing logic in R.equals to compare sets - Issue #599

• Improve list cloning - Issue #595

• Handle multiple inputs with R.allPass and R.anyPass - Issue #604

• Fix R.length wrong logic with inputs as {length: 123} - Issue #606.

• Improve non-curry typings of R.merge by using types from mobily/ts-belt.

• Improve performance of R.uniqWith.

• Wrong R.update if index is -1 - PR #593

• Make R.eqProps safe for falsy inputs - based on this opened Ramda PR.

• Incorrect benchmarks for R.pipe/R.compose - Issue #608

• Fix R.last/R.head typings - Issue #609

6.9.0

• Fix slow R.uniq methods - Issue #581

Fixing R.uniq was done by improving R.indexOf which has performance implication to all methods importing R.indexOf:

• R.includes

• R.intersection

• R.difference

• R.excludes

• R.symmetricDifference

• R.union

• R.without no longer support the following case - without('0:1', ['0', '0:1']) // => ['0']. Now it throws as the first argument should be a list, not a string. Ramda, on the other hand, returns an empty list - https://github.com/ramda/ramda/issues/3086.

6.8.3

• Fix TypeScript build process with rambda/immutable - Issue #572

• Add R.objOf method

• Add R.mapObjIndexed method

• Publish shorter README.md version to NPM

6.8.0

• R.has use Object.prototype.hasOwnProperty- Issue #572

• Expose immutable.ts typings which are Rambda typings with readonly statements - Issue #565

• Fix R.intersection wrong order compared to Ramda.

• R.path wrong return of null instead of undefined when path value is null - PR #577

6.7.0

• Remove ts-toolbelt types from TypeScript definitions. Most affected are the following methods, which lose one of its curried definitions:

1. R.maxBy
2. R.minBy
3. R.pathEq
4. R.viewOr
5. R.when
6. R.merge
7. R.mergeDeepRight
8. R.mergeLeft

6.6.0

• Change R.piped typings to mimic that of R.pipe. Main difference is that R.pipe is focused on unary functions.

• Fix wrong logic when R.without use R.includes while it should use array version of R.includes.

• Use uglify plugin for UMD bundle.

• Remove dist folder from .gitignore in order to fix Deno broken package. Issue #570

• Improve R.fromPairs typings - Issue #567

6.5.3

• Wrong logic where R.without use R.includes while it should use the array version of R.includes

This is Ramda bug, that Rambda also has before this release - https://github.com/ramda/ramda/issues/3086

6.5.2

• Wrong R.defaultTo typings - changes introduced in v6.5.0 are missing their TS equivalent.

• Update dependencies

6.5.1

Fix wrong versions in changelog

6.5.0

• R.defaultTo no longer accepts infinite inputs, thus it follows Ramda implementation.

• R.equals supports equality of functions.

• R.pipe doesn't use R.compose.

• Close Issue #561 - export several internal TS interfaces and types

• Close Issue #559 - improve R.propOr typings

• Add CHANGELOG.md file in release files list

This is only part of the changelog. You can read the full text in CHANGELOG.md file.

❯ Additional info

Most influential contributors(in alphabetical order)

• @farwayer - improving performance in R.find, R.filter; give the idea how to make benchmarks more reliable;

• @thejohnfreeman - add R.assoc, R.chain;

• @peeja - add several methods and fix mutiple issues; provides great MR documentation

• @helmuthdu - add R.clone; help improve code style;

• @jpgorman - add R.zip, R.reject, R.without, R.addIndex;

• @ku8ar - add R.slice, R.propOr, R.identical, R.propIs and several math related methods; introduce the idea to display missing Ramda methods;

• @romgrk - add R.groupBy, R.indexBy, R.findLast, R.findLastIndex;

• @squidfunk - add R.assocPath, R.symmetricDifference, R.difference, R.intersperse;

• @synthet1c - add all lenses methods; add R.applySpec, R.converge;

• @vlad-zhukov - help with configuring Rollup, Babel; change export file to use ES module exports;

Rambda references

• Interview with Dejan Totef at SurviveJS blog

• Awesome functional Javascript programming libraries

• Overview of Rambda pros/cons

Links to Rambda

• awesome-fp-js

• Web Tools Weekly #280

• awesome-docsify

Deprecated from Used by section

• SAP's Cloud SDK - This repo doesn't uses Rambda since October/2020 commit that removes Rambda

My other libraries

Stargazers over time