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.
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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.