core-js-bundle

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 bundled global version, for more info see core-js documentation.

Changelog

3.44.0 - 2025.07.07

• Changes v3.43.0...v3.44.0 (87 commits)
• Uint8Array to / from base64 and hex stage 3 proposal:
  • Fixed several V8 bugs in Uint8Array.fromHex and Uint8Array.prototype.{ setFromBase64, toBase64, toHex }, thanks @brc-dd
• Joint iteration stage 2.7 proposal:
  • Uses Get in Iterator.zipKeyed, following tc39/proposal-joint-iteration#43
• Iterator sequencing stage 2.7 proposal:
  • Iterator.concat no longer reuses IteratorResult object of concatenated iterators, following tc39/proposal-iterator-sequencing#26
• Iterator chunking stage 2 proposal:
  • Added built-ins:
    • Iterator.prototype.sliding
• Number.prototype.clamp stage 2 proposal:
  • clamp no longer throws an error on NaN as min or max, following tc39/proposal-math-clamp#d2387791c265edf66fbe2455eab919016717ce6f
• Fixed some cases of Set.prototype.{ symmetricDifference, union } detection
• Added missing dependencies to some entries of static Iterator methods
• Added missing /full/{ instance, number/virtual }/clamp entries
• Some minor stylistic changes
• Compat data improvements:
  • Added Electron 38 and 39 compat data mapping
  • Added Oculus Quest Browser 38 and 39 compat data mapping
  • Iterator helpers marked as fixed and updated following the latest spec changes in Safari 26.0
  • Set.prototype.{ difference, symmetricDifference, union } marked as fixed in Safari 26.0
  • SuppressedError marked as fixed in FF141
  • Error.isError marked as fixed in Node 24.3
  • setImmediate and clearImmediate marked as available from Deno 2.4
  • Math.sumPrecise marked as shipped in Bun 1.2.18
  • %TypedArray%.prototype.with marked as fixed in Bun 1.2.18