github.com/zloirock/core-js @v3.49.0 sqlite

Welcome to our new website, core-js.io, where our documentation is moving!

I highly recommend reading this: So, what's next?

Modular standard library for JavaScript. Includes polyfills for ECMAScript up to 2025: 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@3, babel and a look into the future

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.try(() => 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]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .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.try(() => 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]

Iterator.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .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.try(() => 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.concat([1, 2], function * (i) { while (true) yield i++; }(3))
  .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])

Index

• Usage
• Installation
• postinstall message
• CommonJS API
• Babel
  • @babel/polyfill
  • @babel/preset-env
  • @babel/runtime
• swc
• Configurable level of aggressiveness
• Custom build
• Supported engines and compatibility data
• Features
• ECMAScript
  • ECMAScript: Object
  • ECMAScript: Function
  • ECMAScript: Error
  • ECMAScript: Array
  • ECMAScript: Iterator
  • ECMAScript: String and RegExp
  • ECMAScript: Number
  • ECMAScript: Math
  • ECMAScript: Date
  • ECMAScript: Promise
  • ECMAScript: Symbol
  • ECMAScript: Collections
  • ECMAScript: Explicit Resource Management
  • ECMAScript: Typed Arrays
  • ECMAScript: Reflect
  • ECMAScript: JSON
  • ECMAScript: globalThis
• ECMAScript proposals
  • Finished proposals
  • globalThis
  • Relative indexing method
  • Array.prototype.includes
  • Array.prototype.flat / Array.prototype.flatMap
  • Array find from last
  • Change Array by copy
  • Array grouping
  • Array.fromAsync
  • ArrayBuffer.prototype.transfer and friends
  • Uint8Array to / from base64 and hex
  • Error.isError
  • Explicit Resource Management
  • Float16 methods
  • Iterator helpers
  • Iterator sequencing
  • Object.values / Object.entries
  • Object.fromEntries
  • Object.getOwnPropertyDescriptors
  • Accessible Object.prototype.hasOwnProperty
  • String padding
  • String.prototype.matchAll
  • String.prototype.replaceAll
  • String.prototype.trimStart / String.prototype.trimEnd
  • RegExp s (dotAll) flag
  • RegExp named capture groups
  • RegExp escaping
  • Promise.allSettled
  • Promise.any
  • Promise.prototype.finally
  • Promise.try
  • Promise.withResolvers
  • Symbol.asyncIterator for asynchronous iteration
  • Symbol.prototype.description
  • JSON.parse source text access
  • Well-formed JSON.stringify
  • Well-formed unicode strings
  • New Set methods
  • Map upsert
  • Math.sumPrecise
  • Stage 3 proposals
  • Joint iteration
  • Symbol.metadata for decorators metadata proposal
  • Stage 2.7 proposals
  • Iterator chunking
  • Stage 2 proposals
  • AsyncIterator helpers
  • Iterator.range
  • Array.isTemplateObject
  • Number.prototype.clamp
  • String.dedent
  • Symbol predicates
  • Symbol.customMatcher for extractors
  • Stage 1 proposals
  • Observable
  • New collections methods
  • .of and .from methods on collection constructors
  • compositeKey and compositeSymbol
  • Array filtering
  • Array deduplication
  • DataView get / set Uint8Clamped methods
  • Number.fromString
  • String.cooked
  • String.prototype.codePoints
  • Symbol.customMatcher for pattern matching
  • Stage 0 proposals
  • Function.prototype.demethodize
  • Function.{ isCallable, isConstructor }
  • Pre-stage 0 proposals
  • Reflect metadata
• Web standards
  • self
  • structuredClone
  • Base64 utility methods
  • setTimeout and setInterval
  • setImmediate
  • queueMicrotask
  • URL and URLSearchParams
  • DOMException
  • iterable DOM collections
• Iteration helpers
• Missing polyfills
• Contributing
• Security policy
• Changelog

Usage⬆

Installation:⬆

// global version
npm install --save core-js@3.49.0
// version without global namespace pollution
npm install --save core-js-pure@3.49.0
// bundled global version
npm install --save core-js-bundle@3.49.0

postinstall message⬆

The core-js project needs your help, so the package shows a message about it after installation. If it causes problems for you, you can disable it:

ADBLOCK=true npm install
// or
DISABLE_OPENCOLLECTIVE=true npm install
// or
npm install --loglevel silent

CommonJS API⬆

You can import only-required-for-you polyfills, like in the examples at the top of README.md. Available CommonJS entry points for all polyfilled methods / constructors and namespaces. Just some examples:

``ts // polyfill allcore-js` features, including early-stage proposals: import "core-js"; // or: import "core-js/full"; // polyfill all actual features - stable ES, web standards and stage 3 ES proposals: import "core-js/actual"; // polyfill only stable features - ES and web standards: import "core-js/stable"; // polyfill only stable ES features: import "core-js/es";

// if you want to polyfill Set: // all Set-related features, with ea