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# core-js [](https://gitter.im/zloirock/core-js?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [](https://www.npmjs.com/package/core-js) [](http://npm-stat.com/charts.html?package=core-js&author=&from=2014-11-18) [](https://travis-ci.org/zloirock/core-js) [](https://david-dm.org/zloirock/core-js?type=dev) #### As advertising: the author is looking for a good job :) Modular standard library for JavaScript. Includes polyfills for [ECMAScript 5](#ecmascript-5), [ECMAScript 6](#ecmascript-6): [promises](#ecmascript-6-promise), [symbols](#ecmascript-6-symbol), [collections](#ecmascript-6-collections), iterators, [typed arrays](#ecmascript-6-typed-arrays), [ECMAScript 7+ proposals](#ecmascript-7-proposals), [setImmediate](#setimmediate), etc. Some additional features such as [dictionaries](#dict) or [extended partial application](#partial-application). You can require only needed features or use it without global namespace pollution. [*Example*](http://goo.gl/a2xexl): ```js Array.from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3] '*'.repeat(10); // => '**********' Promise.resolve(32).then(x => console.log(x)); // => 32 setImmediate(x => console.log(x), 42); // => 42 ``` [*Without global namespace pollution*](http://goo.gl/paOHb0): ```js var core = require('core-js/library'); // With a modular system, otherwise use global `core` core.Array.from(new core.Set([1, 2, 3, 2, 1])); // => [1, 2, 3] core.String.repeat('*', 10); // => '**********' core.Promise.resolve(32).then(x => console.log(x)); // => 32 core.setImmediate(x => console.log(x), 42); // => 42 ``` ### Index - [Usage](#usage) - [Basic](#basic) - [CommonJS](#commonjs) - [Custom build](#custom-build-from-the-command-line) - [Supported engines](#supported-engines) - [Features](#features) - [ECMAScript 5](#ecmascript-5) - [ECMAScript 6](#ecmascript-6) - [ECMAScript 6: Object](#ecmascript-6-object) - [ECMAScript 6: Function](#ecmascript-6-function) - [ECMAScript 6: Array](#ecmascript-6-array) - [ECMAScript 6: String](#ecmascript-6-string) - [ECMAScript 6: RegExp](#ecmascript-6-regexp) - [ECMAScript 6: Number](#ecmascript-6-number) - [ECMAScript 6: Math](#ecmascript-6-math) - [ECMAScript 6: Date](#ecmascript-6-date) - [ECMAScript 6: Promise](#ecmascript-6-promise) - [ECMAScript 6: Symbol](#ecmascript-6-symbol) - [ECMAScript 6: Collections](#ecmascript-6-collections) - [ECMAScript 6: Typed Arrays](#ecmascript-6-typed-arrays) - [ECMAScript 6: Reflect](#ecmascript-6-reflect) - [ECMAScript 7+ proposals](#ecmascript-7-proposals) - [stage 4 proposals](#stage-4-proposals) - [stage 3 proposals](#stage-3-proposals) - [stage 2 proposals](#stage-2-proposals) - [stage 1 proposals](#stage-1-proposals) - [stage 0 proposals](#stage-0-proposals) - [pre-stage 0 proposals](#pre-stage-0-proposals) - [Web standards](#web-standards) - [setTimeout / setInterval](#settimeout--setinterval) - [setImmediate](#setimmediate) - [iterable DOM collections](#iterable-dom-collections) - [Non-standard](#non-standard) - [Object](#object) - [Dict](#dict) - [partial application](#partial-application) - [Number Iterator](#number-iterator) - [escaping strings](#escaping-strings) - [delay](#delay) - [helpers for iterators](#helpers-for-iterators) - [Missing polyfills](#missing-polyfills) - [Changelog](./CHANGELOG.md) ## Usage ### Basic ``` npm i core-js bower install core.js ``` ```js // Default require('core-js'); // Without global namespace pollution var core = require('core-js/library'); // Shim only require('core-js/shim'); ``` If you need complete build for browser, use builds from `core-js/client` path: * [default](https://raw.githack.com/zloirock/core-js/v2.5.3/client/core.min.js): Includes all features, standard and non-standard. * [as a library](https://raw.githack.com/zloirock/core-js/v2.5.3/client/library.min.js): Like "default", but does not pollute the global namespace (see [2nd example at the top](#core-js)). * [shim only](https://raw.githack.com/zloirock/core-js/v2.5.3/client/shim.min.js): Only includes the standard methods. Warning: if you use `core-js` with the extension of native objects, require all needed `core-js` modules at the beginning of entry point of your application, otherwise, conflicts may occur. ### CommonJS You can require only needed modules. ```js require('core-js/fn/set'); require('core-js/fn/array/from'); require('core-js/fn/array/find-index'); Array.from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3] [1, 2, NaN, 3, 4].findIndex(isNaN); // => 2 // or, w/o global namespace pollution: var Set = require('core-js/library/fn/set'); var from = require('core-js/library/fn/array/from'); var findIndex = require('core-js/library/fn/array/find-index'); from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3] findIndex([1, 2, NaN, 3, 4], isNaN); // => 2 ``` Available entry points for methods / constructors, as above examples, and namespaces: for example, `core-js/es6/array` (`core-js/library/es6/array`) contains all [ES6 `Array` features](#ecmascript-6-array), `core-js/es6` (`core-js/library/es6`) contains all ES6 features. ##### Caveats when using CommonJS API: * `modules` path is internal API, does not inject all required dependencies and can be changed in minor or patch releases. Use it only for a custom build and / or if you know what are you doing. * `core-js` is extremely modular and uses a lot of very tiny modules, because of that for usage in browsers bundle up `core-js` instead of usage loader for each file, otherwise, you will have hundreds of requests. #### CommonJS and prototype methods without global namespace pollution In the `library` version, we can't pollute prototypes of native constructors. Because of that, prototype methods transformed to static methods like in examples above. `babel` `runtime` transformer also can't transform them. But with transpilers we can use one more trick - [bind operator and virtual methods](https://github.com/zenparsing/es-function-bind). Special for that, available `/virtual/` entry points. Example: ```js import fill from 'core-js/library/fn/array/virtual/fill'; import findIndex from 'core-js/library/fn/array/virtual/find-index'; Array(10)::fill(0).map((a, b) => b * b)::findIndex(it => it && !(it % 8)); // => 4 // or import {fill, findIndex} from 'core-js/library/fn/array/virtual'; Array(10)::fill(0).map((a, b) => b * b)::findIndex(it => it && !(it % 8)); // => 4 ``` ### Custom build (from the command-line) ``` npm i core-js && cd node_modules/core-js && npm i npm run grunt build:core.dict,es6 -- --blacklist=es6.promise,es6.math --library=on --path=custom uglify ``` Where `core.dict` and `es6` are modules (namespaces) names, which will be added to the build, `es6.promise` and `es6.math` are modules (namespaces) names, which will be excluded from the build, `--library=on` is flag for build without global namespace pollution and `custom` is target file name. Available namespaces: for example, `es6.array` contains [ES6 `Array` features](#ecmascript-6-array), `es6` contains all modules whose names start with `es6`. ### Custom build (from external scripts) [`core-js-builder`](https://www.npmjs.com/package/core-js-builder) package exports a function that takes the same parameters as the `build` target from the previous section. This will conditionally include or exclude certain parts of `core-js`: ```js require('core-js-builder')({ modules: ['es6', 'core.dict'], // modules / namespaces blacklist: ['es6.reflect'], /