core-js
Advanced tools
Package description
The core-js npm package is a modular standard library for JavaScript, which includes polyfills for ECMAScript features. It provides reliable polyfills to ensure that code behaves consistently across different environments, including older browsers.
Polyfilling ECMAScript features
This feature allows developers to use the latest ECMAScript features while ensuring backward compatibility with older environments that do not support these features natively.
require('core-js/stable');
// Now you can use ES6 features like Promise in environments that do not support them natively.Polyfilling Web Standards
Core-js can also polyfill web standards, allowing developers to use modern web APIs in environments that have not implemented them.
require('core-js/web');
// This includes polyfills for web standards like DOM collections (e.g., NodeList), timers, and more.Polyfilling Proposals
Developers can experiment with proposed ECMAScript features before they are finalized and adopted into the standard, ensuring forward compatibility.
require('core-js/proposals');
// This will include polyfills for ECMAScript proposals that are not yet part of the standard.Babel-polyfill is a package that provides polyfills necessary for a full ES2015+ environment. It is similar to core-js but is more tightly coupled with Babel's transpilation process.
The es6-shim package provides polyfills for ECMAScript 6 (aka ECMAScript 2015) features. It is similar to core-js but focuses specifically on ES6 features and does not cover proposals or web standards.
The polyfill-service by Financial Times is an online service that provides polyfills based on the user's browser. It is different from core-js in that it is a service rather than a package you include in your project, but it serves a similar purpose in polyfilling features.
Changelog
Iterator
Iterator.fromIterator.prototype.dropIterator.prototype.everyIterator.prototype.filterIterator.prototype.findIterator.prototype.flatMapIterator.prototype.forEachIterator.prototype.mapIterator.prototype.reduceIterator.prototype.someIterator.prototype.takeIterator.prototype.toArrayIterator.prototype.toAsyncIterator.prototype[@@toStringTag]AsyncIterator
AsyncIterator.fromAsyncIterator.prototype.dropAsyncIterator.prototype.everyAsyncIterator.prototype.filterAsyncIterator.prototype.findAsyncIterator.prototype.flatMapAsyncIterator.prototype.forEachAsyncIterator.prototype.mapAsyncIterator.prototype.reduceAsyncIterator.prototype.someAsyncIterator.prototype.takeAsyncIterator.prototype.toArrayAsyncIterator.prototype[@@toStringTag]/actual/ entries, unconditional forced replacement disabled for features that survived to Stage 3.from accept strings, .flatMap throws on strings returned from the callback, proposal-iterator-helpers/244, proposal-iterator-helpers/250.from and .flatMap throws on non-object iterators, proposal-iterator-helpers/253Set methods proposal:
Set.prototype.intersectionSet.prototype.unionSet.prototype.differenceSet.prototype.symmetricDifferenceSet.prototype.isSubsetOfSet.prototype.isSupersetOfSet.prototype.isDisjointFromSet-like objects as an argument, not all iterablesSets as this, no @@species support, and other minor changes/actual/ entries, unconditional forced replacement changed to feature detection/actual/ namespace)/full/ namespace), those methods are available with fallbacks to old semantics (in addition to Set-like, they accept iterable objects). This behavior will be removed from the next major releaseString.prototype.isWellFormedString.prototype.toWellFormed/actual/ entries, disabled unconditional forced replacementusing statement" and split into 2 (sync and async) proposalsSymbol.disposeSymbol.asyncDisposeSuppressedErrorDisposableStack
DisposableStack.prototype.disposeDisposableStack.prototype.useDisposableStack.prototype.adoptDisposableStack.prototype.deferDisposableStack.prototype.moveDisposableStack.prototype[@@dispose]AsyncDisposableStack
AsyncDisposableStack.prototype.disposeAsyncAsyncDisposableStack.prototype.useAsyncDisposableStack.prototype.adoptAsyncDisposableStack.prototype.deferAsyncDisposableStack.prototype.moveAsyncDisposableStack.prototype[@@asyncDispose]Iterator.prototype[@@dispose]AsyncIterator.prototype[@@asyncDispose]/actual/ namespace entries for Stage 3 proposalString.dedent stage 2 proposal
String.dedentreact-native target for React Native with bundled Hermes.oculus target was renamed to quest.opera_mobile target name is confusing since it contains data for the Chromium-based Android version, but iOS Opera is Safari-based. So opera_mobile target was renamed to opera-android.android target name is also confusing for someone - that means Android WebView, some think thinks that it's Chrome for Android, but they have some differences. For avoiding confusion, added chrome-android target.firefox-android target.oculus and opera_mobile fields are available in the compat data till the next major release.Array.fromAsync marked as supported from Bun 0.3.0String.prototype.{ isWellFormed, toWellFormed } marked as supported from Bun 0.4.0Array by copy proposal marked as supported from Deno 1.27, deno/16429{ Map, WeakMap }.prototype.emplace became stricter by the spec draft@@species pattern) of some .prototype methods from the new collections methods proposal and the Array deduplication proposal that most likely will not be implemented since it contradicts the current TC39 policyNumber constructor, #1154, #1155, thanks @trososset(Timeout|Interval|Immediate) extra arguments fix for Bun 0.3.0- (similarly to IE9-), bun/1633structuredClone, #1156Readme
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.
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, Bitcoin ( bc1qlea7544qtsmj2rayg0lthvza9fau63ux0fstcz ).
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 global version (first 2 examples), for more info see core-js documentation.
FAQs
Standard library
We found that core-js demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
Security News
The Python Software Foundation has secured a 5-year sponsorship from Fastly that supports PSF's activities and events, most notably the security and reliability of the Python Package Index (PyPI).
Security News
LDAPjs, an LDAP Client and Server API for Node.js, was decommissioned after its maintainer received an abusive email from a user, raising concerns about this form of abuse as a potential attack vector.
Security News
CISA launched a new project called Vulnrichment to enrich CVEs with details that help prioritize patching and mitigation efforts, as the NVD backlog of unenriched CVEs awaiting analysis surpasses 10,000.