[](https://opencollective.com/core-js) [](https://www.npmjs.com/package/core-js) [](https://npm-stat.com/charts.html?package=core-js&package=core-js-pure&package=core-js-compat&from=2014-11-18) [](https://npm-stat.com/charts.html?package=core-js&package=core-js-pure&package=core-js-compat&from=2014-11-18) [](https://github.com/zloirock/core-js/actions) [](https://github.com/zloirock/core-js/actions)
> Modular standard library for JavaScript. Includes polyfills for [ECMAScript up to 2021](https://github.com/zloirock/core-js#ecmascript): [promises](https://github.com/zloirock/core-js#ecmascript-promise), [symbols](https://github.com/zloirock/core-js#ecmascript-symbol), [collections](https://github.com/zloirock/core-js#ecmascript-collections), iterators, [typed arrays](https://github.com/zloirock/core-js#ecmascript-typed-arrays), many other features, [ECMAScript proposals](https://github.com/zloirock/core-js#ecmascript-proposals), [some cross-platform WHATWG / W3C features and proposals](#web-standards) like [`URL`](https://github.com/zloirock/core-js#url-and-urlsearchparams). You can load only required features or use it without global namespace pollution.
## As advertising: the author is looking for a good job -)
## [core-js@3, babel and a look into the future](https://github.com/zloirock/core-js/tree/master/docs/2019-03-19-core-js-3-babel-and-a-look-into-the-future.md)
## Raising funds
`core-js` isn't backed by a company, so the future of this project depends on you. Become a sponsor or a backer if you are interested in `core-js`: [**Open Collective**](https://opencollective.com/core-js), [**Patreon**](https://patreon.com/zloirock), **Bitcoin ( bc1qlea7544qtsmj2rayg0lthvza9fau63ux0fstcz )**.
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[*Example of usage*](https://is.gd/XD4mRe):
```js
import 'core-js/actual'; // <- at the top of your entry point
Array.from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3]
[1, 2, 3, 4, 5].groupBy(it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }
Promise.resolve(42).then(x => console.log(x)); // => 42
structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])
queueMicrotask(() => console.log('called as microtask'));
```
*You can load only required features*:
```js
import 'core-js/actual/array/from'; // <- at the top of your entry point
import 'core-js/actual/array/group-by'; // <- at the top of your entry point
import 'core-js/actual/set'; // <- at the top of your entry point
import 'core-js/actual/promise'; // <- at the top of your entry point
import 'core-js/actual/structured-clone'; // <- at the top of your entry point
import 'core-js/actual/queue-microtask'; // <- at the top of your entry point
Array.from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3]
[1, 2, 3, 4, 5].groupBy(it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }
Promise.resolve(42).then(x => console.log(x)); // => 42
structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])
queueMicrotask(() => console.log('called as microtask'));
```
*Or use it without global namespace pollution*:
```js
import from from 'core-js-pure/actual/array/from';
import groupBy from 'core-js-pure/actual/array/group-by';
import Set from 'core-js-pure/actual/set';
import Promise from 'core-js-pure/actual/promise';
import structuredClone from 'core-js-pure/actual/structured-clone';
import queueMicrotask from 'core-js-pure/actual/queue-microtask';
from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3]
groupBy([1, 2, 3, 4, 5], it => it % 2); // => { 1: [1, 3, 5], 0: [2, 4] }
Promise.resolve(42).then(x => console.log(x)); // => 42
structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])
queueMicrotask(() => console.log('called as microtask'));
```
**It's a global version (first 2 examples), for more info see [`core-js` documentation](https://github.com/zloirock/core-js/blob/master/README.md).**