Awesome
ts-extras 
Essential utilities for TypeScript projects
Ideas for additional essential utilities welcome. Type-only utilities belong in type-fest.
Install
npm install ts-extras
Usage
import {isDefined} from 'ts-extras';
[1, undefined, 2].filter(isDefined);
//=> [1, 2]
API
General
asWritable- Cast the given value to beWritable.safeCastTo- Cast a value to the given type safely.
Type guard
isDefined- Check whether a value is defined (notundefined).isPresent- Check whether a value is present (notnullorundefined).isEmpty- Check whether an array is empty.assertError- Assert that the given value is anError.isInfinite- Check whether a value is infinite.
Improved builtin
arrayIncludes- An alternative toArray#includes()that properly acts as a type guard.setHas- An alternative toSet#has()that properly acts as a type guard.objectKeys- A strongly-typed version ofObject.keys().objectEntries- A strongly-typed version ofObject.entries().objectFromEntries- A strongly-typed version ofObject.fromEntries().objectHasOwn- A strongly-typed version ofObject.hasOwn().isFinite- A strongly-typed version ofNumber.isFinite().isInteger- A strongly-typed version ofNumber.isInteger().isSafeInteger- A strongly-typed version ofNumber.isSafeInteger().
FAQ
What is the difference between this and type-fest?
The type-fest package contains only types, meaning they are only used at compile-time and nothing is ever compiled into actual JavaScript code. This package contains functions that are compiled into JavaScript code and used at runtime.