Modularization
On-demand loading and no global namespace pollution
Widely used
Most popular polyfill of the JavaScript. 250 million downloads per month on NPM
Easy to use
Integration with tools like Babel and SWC
Powerful features
Implemented new APIs from ES5 to ongoing ECMAScript proposal
Sponsors
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.
Examples
//https://tinyurl.com/2mknex43
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])
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])
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])
import "https://deno.land/x/corejs@v3.31.1/index.js"; // <- at the top of your entry point
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])