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.
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core-js@3, babel and a look into the future
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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].group(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:
import 'core-js/actual/array/from'; // <- at the top of your entry point
import 'core-js/actual/array/group'; // <- 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].group(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:
import from from 'core-js-pure/actual/array/from';
import group from 'core-js-pure/actual/array/group';
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]
group([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 version without global namespace pollution (the third example), for more info see core-js documentation.