Awesome

ko-projections

NOTICE: This repo is deprecated. Prefer the following pattern.

import { flow } from 'lodash'
import { map, filter } from 'lodash/fp'
import ko from 'knockout'

const flippedAndFilteredFoos = ko.pureComputed(() => flow(
  map((foo) => {
    foo.text = foo.text.split('').reverse().join('')
    return foo
  }),
  filter((foo) => foo.id % 2 === (wantsOdds() ? 1 : 0))
)(foos))

Usage

const foos = ko.observableArray([
  { id: 1, text: 'foo' },
  { id: 2, text: 'bar' },
  { id: 3, text: 'baz' },
  { id: 4, text: 'qux' }
]).extend({
  _: true
})

const wantsOdds = ko.observable(true)

const flippedAndFilteredFoos = foos
  ._.map((foo) => {
    foo.text = foo.text.split('').reverse().join('')
    return foo
  })
  ._.filter((foo) =>
    foo.id % 2 === (wantsOdds() ? 1 : 0))

flippedAndFilteredFoos()
// { id: 1, text: 'oof' },
// { id: 3, text: 'zab' }

wantsOdds(false)

flippedAndFilteredFoos()
// { id: 2, text: 'rab' },
// { id: 4, text: 'xuq' }