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For Yarn 2+ docs and migration guide, see yarnpkg.com.

Package detail

core-js

zloirock146.2mMIT3.42.0TypeScript support: definitely-typed

Standard library

ES3, ES5, ES6, ES7, ES2015, ES2016, ES2017, ES2018, ES2019, ES2020, ES2021, ES2022, ES2023, ES2024, ECMAScript 3, ECMAScript 5, ECMAScript 6, ECMAScript 7, ECMAScript 2015, ECMAScript 2016, ECMAScript 2017, ECMAScript 2018, ECMAScript 2019, ECMAScript 2020, ECMAScript 2021, ECMAScript 2022, ECMAScript 2023, ECMAScript 2024, Map, Set, WeakMap, WeakSet, TypedArray, Promise, Observable, Symbol, Iterator, AsyncIterator, URL, URLSearchParams, queueMicrotask, setImmediate, structuredClone, polyfill, ponyfill, shim

readme

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fundraising PRs welcome version core-js downloads

I highly recommend reading this: So, what's next?

Modular standard library for JavaScript. Includes polyfills for ECMAScript up to 2023: promises, symbols, collections, iterators, typed arrays, many other features, ECMAScript proposals, some cross-platform WHATWG / W3C features and proposals like URL. You can load only required features or use it without global namespace pollution.

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, Patreon, Boosty, Bitcoin ( bc1qlea7544qtsmj2rayg0lthvza9fau63ux0fstcz ), Alipay.




Example of usage:

import 'core-js/actual';

Promise.resolve(42).then(it => console.log(it)); // => 42

Array.from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

[1, 2].flatMap(it => [it, it]); // => [1, 1, 2, 2]

(function * (i) { while (true) yield i++; })(1)
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

You can load only required features:

import 'core-js/actual/promise';
import 'core-js/actual/set';
import 'core-js/actual/iterator';
import 'core-js/actual/array/from';
import 'core-js/actual/array/flat-map';
import 'core-js/actual/structured-clone';

Promise.resolve(42).then(it => console.log(it)); // => 42

Array.from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

[1, 2].flatMap(it => [it, it]); // => [1, 1, 2, 2]

(function * (i) { while (true) yield i++; })(1)
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

Or use it without global namespace pollution:

import Promise from 'core-js-pure/actual/promise';
import Set from 'core-js-pure/actual/set';
import Iterator from 'core-js-pure/actual/iterator';
import from from 'core-js-pure/actual/array/from';
import flatMap from 'core-js-pure/actual/array/flat-map';
import structuredClone from 'core-js-pure/actual/structured-clone';

Promise.resolve(42).then(it => console.log(it)); // => 42

from(new Set([1, 2, 3]).union(new Set([3, 4, 5]))); // => [1, 2, 3, 4, 5]

flatMap([1, 2], it => [it, it]); // => [1, 1, 2, 2]

Iterator.from(function * (i) { while (true) yield i++; }(1))
  .drop(1).take(5)
  .filter(it => it % 2)
  .map(it => it ** 2)
  .toArray(); // => [9, 25]

structuredClone(new Set([1, 2, 3])); // => new Set([1, 2, 3])

It's a global version (first 2 examples), for more info see core-js documentation.