# core-js [![Sponsors on Open Collective](https://opencollective.com/core-js/sponsors/badge.svg)](#raising-funds) [![Backers on Open Collective](https://opencollective.com/core-js/backers/badge.svg)](#raising-funds) [![Gitter](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/zloirock/core-js?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge) [![version](https://img.shields.io/npm/v/core-js.svg)](https://www.npmjs.com/package/core-js) [![npm downloads](https://img.shields.io/npm/dm/core-js.svg)](http://npm-stat.com/charts.html?package=core-js&author=&from=2014-11-18) [![Build Status](https://travis-ci.org/zloirock/core-js.svg)](https://travis-ci.org/zloirock/core-js) [![devDependency status](https://david-dm.org/zloirock/core-js/dev-status.svg)](https://david-dm.org/zloirock/core-js?type=dev) ## As advertising: the author is looking for a good job :) ## [core-js@3, babel and a look into the future](https://github.com/zloirock/core-js/tree/master/docs/2019-03-19-core-js-3-babel-and-a-look-into-the-future.md) ## 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 [**on Open Collective**](https://opencollective.com/core-js) or [**on Patreon**](https://www.patreon.com/zloirock) if you are interested in `core-js`. --- --- --- **It's documentation for obsolete `core-js@2`. If you looking documentation for actual `core-js` version, please, check [this branch](https://github.com/zloirock/core-js/tree/master).** 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/v2.6.9/client/core.min.js): Includes all features, standard and non-standard. * [as a library](https://raw.githack.com/zloirock/core-js/v2.6.9/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/v2.6.9/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'], // blacklist of modules / namespaces, by default - empty list library: false, // flag for build without global namespace pollution, by default - false umd: true // use UMD wrapper for export `core` object, by default - true }).then(code => { // ... }).catch(error => { // ... }); ``` ## Supported engines **Tested in:** - Chrome 26+ - Firefox 4+ - Safari 5+ - Opera 12+ - Internet Explorer 6+ (sure, IE8- with ES3 limitations) - Edge - Android Browser 2.3+ - iOS Safari 5.1+ - PhantomJS 1.9 / 2.1 - NodeJS 0.8+ ...and it doesn't mean `core-js` will not work in other engines, they just have not been tested. ## Features: [*CommonJS entry points:*](#commonjs) ``` core-js(/library) <- all features core-js(/library)/shim <- only polyfills ``` ### ECMAScript 5 All features moved to the [`es6` namespace](#ecmascript-6), here just a list of features: ```js Object .create(proto | null, descriptors?) -> object .getPrototypeOf(object) -> proto | null .defineProperty(target, key, desc) -> target, cap for ie8- .defineProperties(target, descriptors) -> target, cap for ie8- .getOwnPropertyDescriptor(object, key) -> desc .getOwnPropertyNames(object) -> array .keys(object) -> array .seal(object) -> object, cap for ie8- .freeze(object) -> object, cap for ie8- .preventExtensions(object) -> object, cap for ie8- .isSealed(object) -> bool, cap for ie8- .isFrozen(object) -> bool, cap for ie8- .isExtensible(object) -> bool, cap for ie8- Array .isArray(var) -> bool #slice(start?, end?) -> array, fix for ie7- #join(string = ',') -> string, fix for ie7- #indexOf(var, from?) -> int #lastIndexOf(var, from?) -> int #every(fn(val, index, @), that) -> bool #some(fn(val, index, @), that) -> bool #forEach(fn(val, index, @), that) -> void #map(fn(val, index, @), that) -> array #filter(fn(val, index, @), that) -> array #reduce(fn(memo, val, index, @), memo?) -> var #reduceRight(fn(memo, val, index, @), memo?) -> var #sort(fn?) -> @, fixes for some engines Function #bind(object, ...args) -> boundFn(...args) String #split(separator, limit) -> array #trim() -> str RegExp #toString() -> str Number #toFixed(digits) -> string #toPrecision(precision) -> string parseInt(str, radix) -> int parseFloat(str) -> num Date .now() -> int #toISOString() -> string #toJSON() -> string ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es5 ``` ### ECMAScript 6 [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6 ``` #### ECMAScript 6: Object Modules [`es6.object.assign`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.assign.js), [`es6.object.is`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.is.js), [`es6.object.set-prototype-of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.set-prototype-of.js) and [`es6.object.to-string`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.to-string.js). In ES6 most `Object` static methods should work with primitives. Modules [`es6.object.freeze`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.freeze.js), [`es6.object.seal`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.seal.js), [`es6.object.prevent-extensions`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.prevent-extensions.js), [`es6.object.is-frozen`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.is-frozen.js), [`es6.object.is-sealed`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.is-sealed.js), [`es6.object.is-extensible`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.is-extensible.js), [`es6.object.get-own-property-descriptor`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.get-own-property-descriptor.js), [`es6.object.get-prototype-of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.get-prototype-of.js), [`es6.object.keys`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.keys.js) and [`es6.object.get-own-property-names`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.get-own-property-names.js). Just ES5 features: [`es6.object.create`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.create.js), [`es6.object.define-property`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.define-property.js) and [`es6.object.define-properties`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.object.es6.object.define-properties.js). ```js Object .assign(target, ...src) -> target .is(a, b) -> bool .setPrototypeOf(target, proto | null) -> target (required __proto__ - IE11+) .create(object | null, descriptors?) -> object .getPrototypeOf(var) -> object | null .defineProperty(object, key, desc) -> target .defineProperties(object, descriptors) -> target .getOwnPropertyDescriptor(var, key) -> desc | undefined .keys(var) -> array .getOwnPropertyNames(var) -> array .freeze(var) -> var .seal(var) -> var .preventExtensions(var) -> var .isFrozen(var) -> bool .isSealed(var) -> bool .isExtensible(var) -> bool #toString() -> string, ES6 fix: @@toStringTag support ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/object core-js(/library)/fn/object/assign core-js(/library)/fn/object/is core-js(/library)/fn/object/set-prototype-of core-js(/library)/fn/object/get-prototype-of core-js(/library)/fn/object/create core-js(/library)/fn/object/define-property core-js(/library)/fn/object/define-properties core-js(/library)/fn/object/get-own-property-descriptor core-js(/library)/fn/object/keys core-js(/library)/fn/object/get-own-property-names core-js(/library)/fn/object/freeze core-js(/library)/fn/object/seal core-js(/library)/fn/object/prevent-extensions core-js(/library)/fn/object/is-frozen core-js(/library)/fn/object/is-sealed core-js(/library)/fn/object/is-extensible core-js/fn/object/to-string ``` [*Examples*](http://goo.gl/ywdwPz): ```js var foo = {q: 1, w: 2} , bar = {e: 3, r: 4} , baz = {t: 5, y: 6}; Object.assign(foo, bar, baz); // => foo = {q: 1, w: 2, e: 3, r: 4, t: 5, y: 6} Object.is(NaN, NaN); // => true Object.is(0, -0); // => false Object.is(42, 42); // => true Object.is(42, '42'); // => false function Parent(){} function Child(){} Object.setPrototypeOf(Child.prototype, Parent.prototype); new Child instanceof Child; // => true new Child instanceof Parent; // => true var O = {}; O[Symbol.toStringTag] = 'Foo'; '' + O; // => '[object Foo]' Object.keys('qwe'); // => ['0', '1', '2'] Object.getPrototypeOf('qwe') === String.prototype; // => true ``` #### ECMAScript 6: Function Modules [`es6.function.name`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.function.name.js), [`es6.function.has-instance`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.function.has-instance.js). Just ES5: [`es6.function.bind`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.function.bind.js). ```js Function #bind(object, ...args) -> boundFn(...args) #name -> string (IE9+) #@@hasInstance(var) -> bool ``` [*CommonJS entry points:*](#commonjs) ``` core-js/es6/function core-js/fn/function/name core-js/fn/function/has-instance core-js/fn/function/bind core-js/fn/function/virtual/bind ``` [*Example*](http://goo.gl/zqu3Wp): ```js (function foo(){}).name // => 'foo' console.log.bind(console, 42)(43); // => 42 43 ``` #### ECMAScript 6: Array Modules [`es6.array.from`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.from.js), [`es6.array.of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.of.js), [`es6.array.copy-within`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.copy-within.js), [`es6.array.fill`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.fill.js), [`es6.array.find`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.find.js), [`es6.array.find-index`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.find-index.js), [`es6.array.iterator`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.iterator.js). ES5 features with fixes: [`es6.array.is-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.is-array.js), [`es6.array.slice`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.slice.js), [`es6.array.join`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.join.js), [`es6.array.index-of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.index-of.js), [`es6.array.last-index-of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.last-index-of.js), [`es6.array.every`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.every.js), [`es6.array.some`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.some.js), [`es6.array.for-each`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.for-each.js), [`es6.array.map`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.map.js), [`es6.array.filter`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.filter.js), [`es6.array.reduce`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.reduce.js), [`es6.array.reduce-right`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.reduce-right.js), [`es6.array.sort`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.array.sort.js). ```js Array .from(iterable | array-like, mapFn(val, index)?, that) -> array .of(...args) -> array .isArray(var) -> bool #copyWithin(target = 0, start = 0, end = @length) -> @ #fill(val, start = 0, end = @length) -> @ #find(fn(val, index, @), that) -> val #findIndex(fn(val, index, @), that) -> index | -1 #values() -> iterator #keys() -> iterator #entries() -> iterator #join(string = ',') -> string, fix for ie7- #slice(start?, end?) -> array, fix for ie7- #indexOf(var, from?) -> index | -1 #lastIndexOf(var, from?) -> index | -1 #every(fn(val, index, @), that) -> bool #some(fn(val, index, @), that) -> bool #forEach(fn(val, index, @), that) -> void #map(fn(val, index, @), that) -> array #filter(fn(val, index, @), that) -> array #reduce(fn(memo, val, index, @), memo?) -> var #reduceRight(fn(memo, val, index, @), memo?) -> var #sort(fn?) -> @, invalid arguments fix #@@iterator() -> iterator (values) #@@unscopables -> object (cap) Arguments #@@iterator() -> iterator (values, available only in core-js methods) ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/array core-js(/library)/fn/array/from core-js(/library)/fn/array/of core-js(/library)/fn/array/is-array core-js(/library)/fn/array/iterator core-js(/library)/fn/array/copy-within core-js(/library)/fn/array/fill core-js(/library)/fn/array/find core-js(/library)/fn/array/find-index core-js(/library)/fn/array/values core-js(/library)/fn/array/keys core-js(/library)/fn/array/entries core-js(/library)/fn/array/slice core-js(/library)/fn/array/join core-js(/library)/fn/array/index-of core-js(/library)/fn/array/last-index-of core-js(/library)/fn/array/every core-js(/library)/fn/array/some core-js(/library)/fn/array/for-each core-js(/library)/fn/array/map core-js(/library)/fn/array/filter core-js(/library)/fn/array/reduce core-js(/library)/fn/array/reduce-right core-js(/library)/fn/array/sort core-js(/library)/fn/array/virtual/iterator core-js(/library)/fn/array/virtual/copy-within core-js(/library)/fn/array/virtual/fill core-js(/library)/fn/array/virtual/find core-js(/library)/fn/array/virtual/find-index core-js(/library)/fn/array/virtual/values core-js(/library)/fn/array/virtual/keys core-js(/library)/fn/array/virtual/entries core-js(/library)/fn/array/virtual/slice core-js(/library)/fn/array/virtual/join core-js(/library)/fn/array/virtual/index-of core-js(/library)/fn/array/virtual/last-index-of core-js(/library)/fn/array/virtual/every core-js(/library)/fn/array/virtual/some core-js(/library)/fn/array/virtual/for-each core-js(/library)/fn/array/virtual/map core-js(/library)/fn/array/virtual/filter core-js(/library)/fn/array/virtual/reduce core-js(/library)/fn/array/virtual/reduce-right core-js(/library)/fn/array/virtual/sort ``` [*Examples*](http://goo.gl/oaUFUf): ```js Array.from(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3] Array.from({0: 1, 1: 2, 2: 3, length: 3}); // => [1, 2, 3] Array.from('123', Number); // => [1, 2, 3] Array.from('123', function(it){ return it * it; }); // => [1, 4, 9] Array.of(1); // => [1] Array.of(1, 2, 3); // => [1, 2, 3] var array = ['a', 'b', 'c']; for(var val of array)console.log(val); // => 'a', 'b', 'c' for(var val of array.values())console.log(val); // => 'a', 'b', 'c' for(var key of array.keys())console.log(key); // => 0, 1, 2 for(var [key, val] of array.entries()){ console.log(key); // => 0, 1, 2 console.log(val); // => 'a', 'b', 'c' } function isOdd(val){ return val % 2; } [4, 8, 15, 16, 23, 42].find(isOdd); // => 15 [4, 8, 15, 16, 23, 42].findIndex(isOdd); // => 2 [4, 8, 15, 16, 23, 42].find(isNaN); // => undefined [4, 8, 15, 16, 23, 42].findIndex(isNaN); // => -1 Array(5).fill(42); // => [42, 42, 42, 42, 42] [1, 2, 3, 4, 5].copyWithin(0, 3); // => [4, 5, 3, 4, 5] ``` #### ECMAScript 6: String Modules [`es6.string.from-code-point`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.from-code-point.js), [`es6.string.raw`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.raw.js), [`es6.string.iterator`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.iterator.js), [`es6.string.code-point-at`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.code-point-at.js), [`es6.string.ends-with`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.ends-with.js), [`es6.string.includes`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.includes.js), [`es6.string.repeat`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.repeat.js), [`es6.string.starts-with`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.starts-with.js) and [`es6.string.trim`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.trim.js). Annex B HTML methods. Ugly, but it's also the part of the spec. Modules [`es6.string.anchor`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.anchor.js), [`es6.string.big`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.big.js), [`es6.string.blink`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.blink.js), [`es6.string.bold`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.bold.js), [`es6.string.fixed`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.fixed.js), [`es6.string.fontcolor`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.fontcolor.js), [`es6.string.fontsize`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.fontsize.js), [`es6.string.italics`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.italics.js), [`es6.string.link`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.link.js), [`es6.string.small`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.small.js), [`es6.string.strike`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.strike.js), [`es6.string.sub`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.sub.js) and [`es6.string.sup`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.string.sup.js). ```js String .fromCodePoint(...codePoints) -> str .raw({raw}, ...substitutions) -> str #includes(str, from?) -> bool #startsWith(str, from?) -> bool #endsWith(str, from?) -> bool #repeat(num) -> str #codePointAt(pos) -> uint #trim() -> str, ES6 fix #anchor(name) -> str #big() -> str #blink() -> str #bold() -> str #fixed() -> str #fontcolor(color) -> str #fontsize(size) -> str #italics() -> str #link(url) -> str #small() -> str #strike() -> str #sub() -> str #sup() -> str #@@iterator() -> iterator (code points) ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/string core-js(/library)/fn/string/from-code-point core-js(/library)/fn/string/raw core-js(/library)/fn/string/includes core-js(/library)/fn/string/starts-with core-js(/library)/fn/string/ends-with core-js(/library)/fn/string/repeat core-js(/library)/fn/string/code-point-at core-js(/library)/fn/string/trim core-js(/library)/fn/string/anchor core-js(/library)/fn/string/big core-js(/library)/fn/string/blink core-js(/library)/fn/string/bold core-js(/library)/fn/string/fixed core-js(/library)/fn/string/fontcolor core-js(/library)/fn/string/fontsize core-js(/library)/fn/string/italics core-js(/library)/fn/string/link core-js(/library)/fn/string/small core-js(/library)/fn/string/strike core-js(/library)/fn/string/sub core-js(/library)/fn/string/sup core-js(/library)/fn/string/iterator core-js(/library)/fn/string/virtual/includes core-js(/library)/fn/string/virtual/starts-with core-js(/library)/fn/string/virtual/ends-with core-js(/library)/fn/string/virtual/repeat core-js(/library)/fn/string/virtual/code-point-at core-js(/library)/fn/string/virtual/trim core-js(/library)/fn/string/virtual/anchor core-js(/library)/fn/string/virtual/big core-js(/library)/fn/string/virtual/blink core-js(/library)/fn/string/virtual/bold core-js(/library)/fn/string/virtual/fixed core-js(/library)/fn/string/virtual/fontcolor core-js(/library)/fn/string/virtual/fontsize core-js(/library)/fn/string/virtual/italics core-js(/library)/fn/string/virtual/link core-js(/library)/fn/string/virtual/small core-js(/library)/fn/string/virtual/strike core-js(/library)/fn/string/virtual/sub core-js(/library)/fn/string/virtual/sup core-js(/library)/fn/string/virtual/iterator ``` [*Examples*](http://goo.gl/3UaQ93): ```js for(var val of 'a𠮷b'){ console.log(val); // => 'a', '𠮷', 'b' } 'foobarbaz'.includes('bar'); // => true 'foobarbaz'.includes('bar', 4); // => false 'foobarbaz'.startsWith('foo'); // => true 'foobarbaz'.startsWith('bar', 3); // => true 'foobarbaz'.endsWith('baz'); // => true 'foobarbaz'.endsWith('bar', 6); // => true 'string'.repeat(3); // => 'stringstringstring' '𠮷'.codePointAt(0); // => 134071 String.fromCodePoint(97, 134071, 98); // => 'a𠮷b' var name = 'Bob'; String.raw`Hi\n${name}!`; // => 'Hi\\nBob!' (ES6 template string syntax) String.raw({raw: 'test'}, 0, 1, 2); // => 't0e1s2t' 'foo'.bold(); // => 'foo' 'bar'.anchor('a"b'); // => 'bar' 'baz'.link('http://example.com'); // => 'baz' ``` #### ECMAScript 6: RegExp Modules [`es6.regexp.constructor`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.regexp.constructor.js) and [`es6.regexp.flags`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.regexp.flags.js). Support well-known [symbols](#ecmascript-6-symbol) `@@match`, `@@replace`, `@@search` and `@@split`, modules [`es6.regexp.match`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.regexp.match.js), [`es6.regexp.replace`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.regexp.replace.js), [`es6.regexp.search`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.regexp.search.js) and [`es6.regexp.split`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.regexp.split.js). ``` [new] RegExp(pattern, flags?) -> regexp, ES6 fix: can alter flags (IE9+) #flags -> str (IE9+) #toString() -> str, ES6 fixes #@@match(str) -> array | null #@@replace(str, replacer) -> string #@@search(str) -> index #@@split(str, limit) -> array String #match(tpl) -> var, ES6 fix for support @@match #replace(tpl, replacer) -> var, ES6 fix for support @@replace #search(tpl) -> var, ES6 fix for support @@search #split(tpl, limit) -> var, ES6 fix for support @@split, some fixes for old engines ``` [*CommonJS entry points:*](#commonjs) ``` core-js/es6/regexp core-js/fn/regexp/constructor core-js(/library)/fn/regexp/flags core-js/fn/regexp/to-string core-js/fn/regexp/match core-js/fn/regexp/replace core-js/fn/regexp/search core-js/fn/regexp/split ``` [*Examples*](http://goo.gl/PiJxBD): ```js RegExp(/./g, 'm'); // => /./m /foo/.flags; // => '' /foo/gim.flags; // => 'gim' 'foo'.match({[Symbol.match]: _ => 1}); // => 1 'foo'.replace({[Symbol.replace]: _ => 2}); // => 2 'foo'.search({[Symbol.search]: _ => 3}); // => 3 'foo'.split({[Symbol.split]: _ => 4}); // => 4 RegExp.prototype.toString.call({source: 'foo', flags: 'bar'}); // => '/foo/bar' ``` #### ECMAScript 6: Number Module [`es6.number.constructor`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.constructor.js). `Number` constructor support binary and octal literals, [*example*](http://goo.gl/jRd6b3): ```js Number('0b1010101'); // => 85 Number('0o7654321'); // => 2054353 ``` Modules [`es6.number.epsilon`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.epsilon.js), [`es6.number.is-finite`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.is-finite.js), [`es6.number.is-integer`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.is-integer.js), [`es6.number.is-nan`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.is-nan.js), [`es6.number.is-safe-integer`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.is-safe-integer.js), [`es6.number.max-safe-integer`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.max-safe-integer.js), [`es6.number.min-safe-integer`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.min-safe-integer.js), [`es6.number.parse-float`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.parse-float.js), [`es6.number.parse-int`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.parse-int.js), [`es6.number.to-fixed`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.to-fixed.js), [`es6.number.to-precision`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.number.to-precision.js), [`es6.parse-int`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.parse-int.js), [`es6.parse-float`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.parse-float.js). ```js [new] Number(var) -> number | number object .isFinite(num) -> bool .isNaN(num) -> bool .isInteger(num) -> bool .isSafeInteger(num) -> bool .parseFloat(str) -> num .parseInt(str) -> int .EPSILON -> num .MAX_SAFE_INTEGER -> int .MIN_SAFE_INTEGER -> int #toFixed(digits) -> string, fixes #toPrecision(precision) -> string, fixes parseFloat(str) -> num, fixes parseInt(str) -> int, fixes ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/number core-js/es6/number/constructor core-js(/library)/fn/number/is-finite core-js(/library)/fn/number/is-nan core-js(/library)/fn/number/is-integer core-js(/library)/fn/number/is-safe-integer core-js(/library)/fn/number/parse-float core-js(/library)/fn/number/parse-int core-js(/library)/fn/number/epsilon core-js(/library)/fn/number/max-safe-integer core-js(/library)/fn/number/min-safe-integer core-js(/library)/fn/number/to-fixed core-js(/library)/fn/number/to-precision core-js(/library)/fn/parse-float core-js(/library)/fn/parse-int ``` #### ECMAScript 6: Math Modules [`es6.math.acosh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.acosh.js), [`es6.math.asinh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.asinh.js), [`es6.math.atanh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.atanh.js), [`es6.math.cbrt`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.cbrt.js), [`es6.math.clz32`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.clz32.js), [`es6.math.cosh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.cosh.js), [`es6.math.expm1`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.expm1.js), [`es6.math.fround`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.fround.js), [`es6.math.hypot`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.hypot.js), [`es6.math.imul`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.imul.js), [`es6.math.log10`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.log10.js), [`es6.math.log1p`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.log1p.js), [`es6.math.log2`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.log2.js), [`es6.math.sign`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.sign.js), [`es6.math.sinh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.sinh.js), [`es6.math.tanh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.tanh.js), [`es6.math.trunc`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.math.trunc.js). ```js Math .acosh(num) -> num .asinh(num) -> num .atanh(num) -> num .cbrt(num) -> num .clz32(num) -> uint .cosh(num) -> num .expm1(num) -> num .fround(num) -> num .hypot(...args) -> num .imul(num, num) -> int .log1p(num) -> num .log10(num) -> num .log2(num) -> num .sign(num) -> 1 | -1 | 0 | -0 | NaN .sinh(num) -> num .tanh(num) -> num .trunc(num) -> num ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/math core-js(/library)/fn/math/acosh core-js(/library)/fn/math/asinh core-js(/library)/fn/math/atanh core-js(/library)/fn/math/cbrt core-js(/library)/fn/math/clz32 core-js(/library)/fn/math/cosh core-js(/library)/fn/math/expm1 core-js(/library)/fn/math/fround core-js(/library)/fn/math/hypot core-js(/library)/fn/math/imul core-js(/library)/fn/math/log1p core-js(/library)/fn/math/log10 core-js(/library)/fn/math/log2 core-js(/library)/fn/math/sign core-js(/library)/fn/math/sinh core-js(/library)/fn/math/tanh core-js(/library)/fn/math/trunc ``` #### ECMAScript 6: Date Modules [`es6.date.to-string`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.date.to-string.js), ES5 features with fixes: [`es6.date.now`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.date.now.js), [`es6.date.to-iso-string`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.date.to-iso-string.js), [`es6.date.to-json`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.date.to-json.js) and [`es6.date.to-primitive`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.date.to-primitive.js). ```js Date .now() -> int #toISOString() -> string #toJSON() -> string #toString() -> string #@@toPrimitive(hint) -> primitive ``` [*CommonJS entry points:*](#commonjs) ``` core-js/es6/date core-js/fn/date/to-string core-js(/library)/fn/date/now core-js(/library)/fn/date/to-iso-string core-js(/library)/fn/date/to-json core-js(/library)/fn/date/to-primitive ``` [*Example*](http://goo.gl/haeHLR): ```js new Date(NaN).toString(); // => 'Invalid Date' ``` #### ECMAScript 6: Promise Module [`es6.promise`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.promise.js). ```js new Promise(executor(resolve(var), reject(var))) -> promise #then(resolved(var), rejected(var)) -> promise #catch(rejected(var)) -> promise .resolve(promise | var) -> promise .reject(var) -> promise .all(iterable) -> promise .race(iterable) -> promise ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/promise core-js(/library)/fn/promise ``` Basic [*example*](http://goo.gl/vGrtUC): ```js function sleepRandom(time){ return new Promise(function(resolve, reject){ setTimeout(resolve, time * 1e3, 0 | Math.random() * 1e3); }); } console.log('Run'); // => Run sleepRandom(5).then(function(result){ console.log(result); // => 869, after 5 sec. return sleepRandom(10); }).then(function(result){ console.log(result); // => 202, after 10 sec. }).then(function(){ console.log('immediately after'); // => immediately after throw Error('Irror!'); }).then(function(){ console.log('will not be displayed'); }).catch(x => console.log(x)); // => => Error: Irror! ``` `Promise.resolve` and `Promise.reject` [*example*](http://goo.gl/vr8TN3): ```js Promise.resolve(42).then(x => console.log(x)); // => 42 Promise.reject(42).catch(x => console.log(x)); // => 42 Promise.resolve($.getJSON('/data.json')); // => ES6 promise ``` `Promise.all` [*example*](http://goo.gl/RdoDBZ): ```js Promise.all([ 'foo', sleepRandom(5), sleepRandom(15), sleepRandom(10) // after 15 sec: ]).then(x => console.log(x)); // => ['foo', 956, 85, 382] ``` `Promise.race` [*example*](http://goo.gl/L8ovkJ): ```js function timeLimit(promise, time){ return Promise.race([promise, new Promise(function(resolve, reject){ setTimeout(reject, time * 1e3, Error('Await > ' + time + ' sec')); })]); } timeLimit(sleepRandom(5), 10).then(x => console.log(x)); // => 853, after 5 sec. timeLimit(sleepRandom(15), 10).catch(x => console.log(x)); // Error: Await > 10 sec ``` ECMAScript 7 [async functions](https://tc39.github.io/ecmascript-asyncawait) [example](http://goo.gl/wnQS4j): ```js var delay = time => new Promise(resolve => setTimeout(resolve, time)) async function sleepRandom(time){ await delay(time * 1e3); return 0 | Math.random() * 1e3; }; async function sleepError(time, msg){ await delay(time * 1e3); throw Error(msg); }; (async () => { try { console.log('Run'); // => Run console.log(await sleepRandom(5)); // => 936, after 5 sec. var [a, b, c] = await Promise.all([ sleepRandom(5), sleepRandom(15), sleepRandom(10) ]); console.log(a, b, c); // => 210 445 71, after 15 sec. await sleepError(5, 'Irror!'); console.log('Will not be displayed'); } catch(e){ console.log(e); // => Error: 'Irror!', after 5 sec. } })(); ``` ##### Unhandled rejection tracking In Node.js, like in native implementation, available events [`unhandledRejection`](https://nodejs.org/api/process.html#process_event_unhandledrejection) and [`rejectionHandled`](https://nodejs.org/api/process.html#process_event_rejectionhandled): ```js process.on('unhandledRejection', (reason, promise) => console.log('unhandled', reason, promise)); process.on('rejectionHandled', (promise) => console.log('handled', promise)); var p = Promise.reject(42); // unhandled 42 [object Promise] setTimeout(() => p.catch(_ => _), 1e3); // handled [object Promise] ``` In a browser on rejection, by default, you will see notify in the console, or you can add a custom handler and a handler on handling unhandled, [*example*](http://goo.gl/Wozskl): ```js window.onunhandledrejection = e => console.log('unhandled', e.reason, e.promise); window.onrejectionhandled = e => console.log('handled', e.reason, e.promise); var p = Promise.reject(42); // unhandled 42 [object Promise] setTimeout(() => p.catch(_ => _), 1e3); // handled 42 [object Promise] ``` #### ECMAScript 6: Symbol Module [`es6.symbol`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.symbol.js). ```js Symbol(description?) -> symbol .hasInstance -> @@hasInstance .isConcatSpreadable -> @@isConcatSpreadable .iterator -> @@iterator .match -> @@match .replace -> @@replace .search -> @@search .species -> @@species .split -> @@split .toPrimitive -> @@toPrimitive .toStringTag -> @@toStringTag .unscopables -> @@unscopables .for(key) -> symbol .keyFor(symbol) -> key .useSimple() -> void .useSetter() -> void Object .getOwnPropertySymbols(object) -> array ``` Also wrapped some methods for correct work with `Symbol` polyfill. ```js Object .create(proto | null, descriptors?) -> object .defineProperty(target, key, desc) -> target .defineProperties(target, descriptors) -> target .getOwnPropertyDescriptor(var, key) -> desc | undefined .getOwnPropertyNames(var) -> array #propertyIsEnumerable(key) -> bool JSON .stringify(target, replacer?, space?) -> string | undefined ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/symbol core-js(/library)/fn/symbol core-js(/library)/fn/symbol/has-instance core-js(/library)/fn/symbol/is-concat-spreadable core-js(/library)/fn/symbol/iterator core-js(/library)/fn/symbol/match core-js(/library)/fn/symbol/replace core-js(/library)/fn/symbol/search core-js(/library)/fn/symbol/species core-js(/library)/fn/symbol/split core-js(/library)/fn/symbol/to-primitive core-js(/library)/fn/symbol/to-string-tag core-js(/library)/fn/symbol/unscopables core-js(/library)/fn/symbol/for core-js(/library)/fn/symbol/key-for ``` [*Basic example*](http://goo.gl/BbvWFc): ```js var Person = (function(){ var NAME = Symbol('name'); function Person(name){ this[NAME] = name; } Person.prototype.getName = function(){ return this[NAME]; }; return Person; })(); var person = new Person('Vasya'); console.log(person.getName()); // => 'Vasya' console.log(person['name']); // => undefined console.log(person[Symbol('name')]); // => undefined, symbols are uniq for(var key in person)console.log(key); // => only 'getName', symbols are not enumerable ``` `Symbol.for` & `Symbol.keyFor` [*example*](http://goo.gl/0pdJjX): ```js var symbol = Symbol.for('key'); symbol === Symbol.for('key'); // true Symbol.keyFor(symbol); // 'key' ``` [*Example*](http://goo.gl/mKVOQJ) with methods for getting own object keys: ```js var O = {a: 1}; Object.defineProperty(O, 'b', {value: 2}); O[Symbol('c')] = 3; Object.keys(O); // => ['a'] Object.getOwnPropertyNames(O); // => ['a', 'b'] Object.getOwnPropertySymbols(O); // => [Symbol(c)] Reflect.ownKeys(O); // => ['a', 'b', Symbol(c)] ``` ##### Caveats when using `Symbol` polyfill: * We can't add new primitive type, `Symbol` returns object. * `Symbol.for` and `Symbol.keyFor` can't be shimmed cross-realm. * By default, to hide the keys, `Symbol` polyfill defines setter in `Object.prototype`. For this reason, uncontrolled creation of symbols can cause memory leak and the `in` operator is not working correctly with `Symbol` polyfill: `Symbol() in {} // => true`. You can disable defining setters in `Object.prototype`. [Example](http://goo.gl/N5UD7J): ```js Symbol.useSimple(); var s1 = Symbol('s1') , o1 = {}; o1[s1] = true; for(var key in o1)console.log(key); // => 'Symbol(s1)_t.qamkg9f3q', w/o native Symbol Symbol.useSetter(); var s2 = Symbol('s2') , o2 = {}; o2[s2] = true; for(var key in o2)console.log(key); // nothing ``` * Currently, `core-js` not adds setters to `Object.prototype` for well-known symbols for correct work something like `Symbol.iterator in foo`. It can cause problems with their enumerability. * Some problems possible with environment exotic objects (for example, IE `localStorage`). #### ECMAScript 6: Collections `core-js` uses native collections in most case, just fixes methods / constructor, if it's required, and in old environment uses fast polyfill (O(1) lookup). #### Map Module [`es6.map`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.map.js). ```js new Map(iterable (entries) ?) -> map #clear() -> void #delete(key) -> bool #forEach(fn(val, key, @), that) -> void #get(key) -> val #has(key) -> bool #set(key, val) -> @ #size -> uint #values() -> iterator #keys() -> iterator #entries() -> iterator #@@iterator() -> iterator (entries) ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/map core-js(/library)/fn/map ``` [*Examples*](http://goo.gl/GWR7NI): ```js var a = [1]; var map = new Map([['a', 1], [42, 2]]); map.set(a, 3).set(true, 4); console.log(map.size); // => 4 console.log(map.has(a)); // => true console.log(map.has([1])); // => false console.log(map.get(a)); // => 3 map.forEach(function(val, key){ console.log(val); // => 1, 2, 3, 4 console.log(key); // => 'a', 42, [1], true }); map.delete(a); console.log(map.size); // => 3 console.log(map.get(a)); // => undefined console.log(Array.from(map)); // => [['a', 1], [42, 2], [true, 4]] var map = new Map([['a', 1], ['b', 2], ['c', 3]]); for(var [key, val] of map){ console.log(key); // => 'a', 'b', 'c' console.log(val); // => 1, 2, 3 } for(var val of map.values())console.log(val); // => 1, 2, 3 for(var key of map.keys())console.log(key); // => 'a', 'b', 'c' for(var [key, val] of map.entries()){ console.log(key); // => 'a', 'b', 'c' console.log(val); // => 1, 2, 3 } ``` #### Set Module [`es6.set`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.set.js). ```js new Set(iterable?) -> set #add(key) -> @ #clear() -> void #delete(key) -> bool #forEach(fn(el, el, @), that) -> void #has(key) -> bool #size -> uint #values() -> iterator #keys() -> iterator #entries() -> iterator #@@iterator() -> iterator (values) ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/set core-js(/library)/fn/set ``` [*Examples*](http://goo.gl/bmhLwg): ```js var set = new Set(['a', 'b', 'a', 'c']); set.add('d').add('b').add('e'); console.log(set.size); // => 5 console.log(set.has('b')); // => true set.forEach(function(it){ console.log(it); // => 'a', 'b', 'c', 'd', 'e' }); set.delete('b'); console.log(set.size); // => 4 console.log(set.has('b')); // => false console.log(Array.from(set)); // => ['a', 'c', 'd', 'e'] var set = new Set([1, 2, 3, 2, 1]); for(var val of set)console.log(val); // => 1, 2, 3 for(var val of set.values())console.log(val); // => 1, 2, 3 for(var key of set.keys())console.log(key); // => 1, 2, 3 for(var [key, val] of set.entries()){ console.log(key); // => 1, 2, 3 console.log(val); // => 1, 2, 3 } ``` #### WeakMap Module [`es6.weak-map`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.weak-map.js). ```js new WeakMap(iterable (entries) ?) -> weakmap #delete(key) -> bool #get(key) -> val #has(key) -> bool #set(key, val) -> @ ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/weak-map core-js(/library)/fn/weak-map ``` [*Examples*](http://goo.gl/SILXyw): ```js var a = [1] , b = [2] , c = [3]; var wmap = new WeakMap([[a, 1], [b, 2]]); wmap.set(c, 3).set(b, 4); console.log(wmap.has(a)); // => true console.log(wmap.has([1])); // => false console.log(wmap.get(a)); // => 1 wmap.delete(a); console.log(wmap.get(a)); // => undefined // Private properties store: var Person = (function(){ var names = new WeakMap; function Person(name){ names.set(this, name); } Person.prototype.getName = function(){ return names.get(this); }; return Person; })(); var person = new Person('Vasya'); console.log(person.getName()); // => 'Vasya' for(var key in person)console.log(key); // => only 'getName' ``` #### WeakSet Module [`es6.weak-set`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.weak-set.js). ```js new WeakSet(iterable?) -> weakset #add(key) -> @ #delete(key) -> bool #has(key) -> bool ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/weak-set core-js(/library)/fn/weak-set ``` [*Examples*](http://goo.gl/TdFbEx): ```js var a = [1] , b = [2] , c = [3]; var wset = new WeakSet([a, b, a]); wset.add(c).add(b).add(c); console.log(wset.has(b)); // => true console.log(wset.has([2])); // => false wset.delete(b); console.log(wset.has(b)); // => false ``` ##### Caveats when using collections polyfill: * Weak-collections polyfill stores values as hidden properties of keys. It works correct and not leak in most cases. However, it is desirable to store a collection longer than its keys. #### ECMAScript 6: Typed Arrays Implementations and fixes `ArrayBuffer`, `DataView`, typed arrays constructors, static and prototype methods. Typed Arrays work only in environments with support descriptors (IE9+), `ArrayBuffer` and `DataView` should work anywhere. Modules [`es6.typed.array-buffer`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.array-buffer.js), [`es6.typed.data-view`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.data-view.js), [`es6.typed.int8-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.int8-array.js), [`es6.typed.uint8-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.uint8-array.js), [`es6.typed.uint8-clamped-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.uint8-clamped-array.js), [`es6.typed.int16-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.int16-array.js), [`es6.typed.uint16-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.uint16-array.js), [`es6.typed.int32-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.int32-array.js), [`es6.typed.uint32-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.uint32-array.js), [`es6.typed.float32-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.float32-array.js) and [`es6.typed.float64-array`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.typed.float64-array.js). ```js new ArrayBuffer(length) -> buffer .isView(var) -> bool #slice(start = 0, end = @length) -> buffer #byteLength -> uint new DataView(buffer, byteOffset = 0, byteLength = buffer.byteLength - byteOffset) -> view #getInt8(offset) -> int8 #getUint8(offset) -> uint8 #getInt16(offset, littleEndian = false) -> int16 #getUint16(offset, littleEndian = false) -> uint16 #getInt32(offset, littleEndian = false) -> int32 #getUint32(offset, littleEndian = false) -> uint32 #getFloat32(offset, littleEndian = false) -> float32 #getFloat64(offset, littleEndian = false) -> float64 #setInt8(offset, value) -> void #setUint8(offset, value) -> void #setInt16(offset, value, littleEndian = false) -> void #setUint16(offset, value, littleEndian = false) -> void #setInt32(offset, value, littleEndian = false) -> void #setUint32(offset, value, littleEndian = false) -> void #setFloat32(offset, value, littleEndian = false) -> void #setFloat64(offset, value, littleEndian = false) -> void #buffer -> buffer #byteLength -> uint #byteOffset -> uint { Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array } new %TypedArray%(length) -> typed new %TypedArray%(typed) -> typed new %TypedArray%(arrayLike) -> typed new %TypedArray%(iterable) -> typed new %TypedArray%(buffer, byteOffset = 0, length = (buffer.byteLength - byteOffset) / @BYTES_PER_ELEMENT) -> typed .BYTES_PER_ELEMENT -> uint .from(arrayLike | iterable, mapFn(val, index)?, that) -> typed .of(...args) -> typed #BYTES_PER_ELEMENT -> uint #copyWithin(target = 0, start = 0, end = @length) -> @ #every(fn(val, index, @), that) -> bool #fill(val, start = 0, end = @length) -> @ #filter(fn(val, index, @), that) -> typed #find(fn(val, index, @), that) -> val #findIndex(fn(val, index, @), that) -> index #forEach(fn(val, index, @), that) -> void #indexOf(var, from?) -> int #join(string = ',') -> string #lastIndexOf(var, from?) -> int #map(fn(val, index, @), that) -> typed #reduce(fn(memo, val, index, @), memo?) -> var #reduceRight(fn(memo, val, index, @), memo?) -> var #reverse() -> @ #set(arrayLike, offset = 0) -> void #slice(start = 0, end = @length) -> typed #some(fn(val, index, @), that) -> bool #sort(fn(a, b)?) -> @ #subarray(start = 0, end = @length) -> typed #toString() -> string #toLocaleString() -> string #values() -> iterator #keys() -> iterator #entries() -> iterator #@@iterator() -> iterator (values) #buffer -> buffer #byteLength -> uint #byteOffset -> uint #length -> uint ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/typed core-js(/library)/fn/typed core-js(/library)/fn/typed/array-buffer core-js(/library)/fn/typed/data-view core-js(/library)/fn/typed/int8-array core-js(/library)/fn/typed/uint8-array core-js(/library)/fn/typed/uint8-clamped-array core-js(/library)/fn/typed/int16-array core-js(/library)/fn/typed/uint16-array core-js(/library)/fn/typed/int32-array core-js(/library)/fn/typed/uint32-array core-js(/library)/fn/typed/float32-array core-js(/library)/fn/typed/float64-array ``` [*Examples*](http://goo.gl/yla75z): ```js new Int32Array(4); // => [0, 0, 0, 0] new Uint8ClampedArray([1, 2, 3, 666]); // => [1, 2, 3, 255] new Float32Array(new Set([1, 2, 3, 2, 1])); // => [1, 2, 3] var buffer = new ArrayBuffer(8); var view = new DataView(buffer); view.setFloat64(0, 123.456, true); new Uint8Array(buffer.slice(4)); // => [47, 221, 94, 64] Int8Array.of(1, 1.5, 5.7, 745); // => [1, 1, 5, -23] Uint8Array.from([1, 1.5, 5.7, 745]); // => [1, 1, 5, 233] var typed = new Uint8Array([1, 2, 3]); var a = typed.slice(1); // => [2, 3] typed.buffer === a.buffer; // => false var b = typed.subarray(1); // => [2, 3] typed.buffer === b.buffer; // => true typed.filter(it => it % 2); // => [1, 3] typed.map(it => it * 1.5); // => [1, 3, 4] for(var val of typed)console.log(val); // => 1, 2, 3 for(var val of typed.values())console.log(val); // => 1, 2, 3 for(var key of typed.keys())console.log(key); // => 0, 1, 2 for(var [key, val] of typed.entries()){ console.log(key); // => 0, 1, 2 console.log(val); // => 1, 2, 3 } ``` ##### Caveats when using typed arrays: * Typed Arrays polyfills works completely how should work by the spec, but because of internal use getter / setters on each instance, is slow and consumes significant memory. However, typed arrays polyfills required mainly for IE9 (and for `Uint8ClampedArray` in IE10 and early IE11), all modern engines have native typed arrays and requires only constructors fixes and methods. * The current version hasn't special entry points for methods, they can be added only with constructors. It can be added in the future. * In the `library` version we can't pollute native prototypes, so prototype methods available as constructors static. #### ECMAScript 6: Reflect Modules [`es6.reflect.apply`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.apply.js), [`es6.reflect.construct`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.construct.js), [`es6.reflect.define-property`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.define-property.js), [`es6.reflect.delete-property`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.delete-property.js), [`es6.reflect.enumerate`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.enumerate.js), [`es6.reflect.get`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.get.js), [`es6.reflect.get-own-property-descriptor`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.get-own-property-descriptor.js), [`es6.reflect.get-prototype-of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.get-prototype-of.js), [`es6.reflect.has`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.has.js), [`es6.reflect.is-extensible`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.is-extensible.js), [`es6.reflect.own-keys`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.own-keys.js), [`es6.reflect.prevent-extensions`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.prevent-extensions.js), [`es6.reflect.set`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.set.js), [`es6.reflect.set-prototype-of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es6.reflect.set-prototype-of.js). ```js Reflect .apply(target, thisArgument, argumentsList) -> var .construct(target, argumentsList, newTarget?) -> object .defineProperty(target, propertyKey, attributes) -> bool .deleteProperty(target, propertyKey) -> bool .enumerate(target) -> iterator (removed from the spec and will be removed from core-js@3) .get(target, propertyKey, receiver?) -> var .getOwnPropertyDescriptor(target, propertyKey) -> desc .getPrototypeOf(target) -> object | null .has(target, propertyKey) -> bool .isExtensible(target) -> bool .ownKeys(target) -> array .preventExtensions(target) -> bool .set(target, propertyKey, V, receiver?) -> bool .setPrototypeOf(target, proto) -> bool (required __proto__ - IE11+) ``` [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es6/reflect core-js(/library)/fn/reflect core-js(/library)/fn/reflect/apply core-js(/library)/fn/reflect/construct core-js(/library)/fn/reflect/define-property core-js(/library)/fn/reflect/delete-property core-js(/library)/fn/reflect/enumerate (deprecated and will be removed from the next major release) core-js(/library)/fn/reflect/get core-js(/library)/fn/reflect/get-own-property-descriptor core-js(/library)/fn/reflect/get-prototype-of core-js(/library)/fn/reflect/has core-js(/library)/fn/reflect/is-extensible core-js(/library)/fn/reflect/own-keys core-js(/library)/fn/reflect/prevent-extensions core-js(/library)/fn/reflect/set core-js(/library)/fn/reflect/set-prototype-of ``` [*Examples*](http://goo.gl/gVT0cH): ```js var O = {a: 1}; Object.defineProperty(O, 'b', {value: 2}); O[Symbol('c')] = 3; Reflect.ownKeys(O); // => ['a', 'b', Symbol(c)] function C(a, b){ this.c = a + b; } var instance = Reflect.construct(C, [20, 22]); instance.c; // => 42 ``` ### ECMAScript 7+ proposals [The TC39 process.](https://tc39.github.io/process-document/) [*CommonJS entry points:*](#commonjs) ``` core-js(/library)/es7 core-js(/library)/es7/array core-js(/library)/es7/global core-js(/library)/es7/string core-js(/library)/es7/map core-js(/library)/es7/set core-js(/library)/es7/error core-js(/library)/es7/math core-js(/library)/es7/system core-js(/library)/es7/symbol core-js(/library)/es7/reflect core-js(/library)/es7/observable ``` `core-js/stage/4` entry point contains only stage 4 proposals, `core-js/stage/3` - stage 3 and stage 4, etc. #### Stage 4 proposals [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/stage/4 ``` * `{Array, %TypedArray%}#includes` [proposal](https://github.com/tc39/Array.prototype.includes) - module [`es7.array.includes`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.array.includes.js), `%TypedArray%` version in modules from [this section](#ecmascript-6-typed-arrays). ```js Array #includes(var, from?) -> bool { Int8Array, Uint8Array, Uint8ClampedArray, Int16Array, Uint16Array, Int32Array, Uint32Array, Float32Array, Float64Array } #includes(var, from?) -> bool ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/array/includes ``` [*Examples*](http://goo.gl/2Gq4ma): ```js [1, 2, 3].includes(2); // => true [1, 2, 3].includes(4); // => false [1, 2, 3].includes(2, 2); // => false [NaN].indexOf(NaN); // => -1 [NaN].includes(NaN); // => true Array(1).indexOf(undefined); // => -1 Array(1).includes(undefined); // => true ``` * `Object.values`, `Object.entries` [proposal](https://github.com/tc39/proposal-object-values-entries) - modules [`es7.object.values`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.values.js), [`es7.object.entries`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.entries.js) ```js Object .values(object) -> array .entries(object) -> array ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/object/values core-js(/library)/fn/object/entries ``` [*Examples*](http://goo.gl/6kuGOn): ```js Object.values({a: 1, b: 2, c: 3}); // => [1, 2, 3] Object.entries({a: 1, b: 2, c: 3}); // => [['a', 1], ['b', 2], ['c', 3]] for(let [key, value] of Object.entries({a: 1, b: 2, c: 3})){ console.log(key); // => 'a', 'b', 'c' console.log(value); // => 1, 2, 3 } ``` * `Object.getOwnPropertyDescriptors` [proposal](https://github.com/tc39/proposal-object-getownpropertydescriptors) - module [`es7.object.get-own-property-descriptors`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.get-own-property-descriptors.js) ```js Object .getOwnPropertyDescriptors(object) -> object ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/object/get-own-property-descriptors ``` *Examples*: ```js // Shallow object cloning with prototype and descriptors: var copy = Object.create(Object.getPrototypeOf(O), Object.getOwnPropertyDescriptors(O)); // Mixin: Object.defineProperties(target, Object.getOwnPropertyDescriptors(source)); ``` * `String#padStart`, `String#padEnd` [proposal](https://github.com/tc39/proposal-string-pad-start-end) - modules [`es7.string.pad-start`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.string.pad-start.js), [`es7.string.pad-end`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.string.pad-end.js) ```js String #padStart(length, fillStr = ' ') -> string #padEnd(length, fillStr = ' ') -> string ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/string/pad-start core-js(/library)/fn/string/pad-end core-js(/library)/fn/string/virtual/pad-start core-js(/library)/fn/string/virtual/pad-end ``` [*Examples*](http://goo.gl/hK5ccv): ```js 'hello'.padStart(10); // => ' hello' 'hello'.padStart(10, '1234'); // => '12341hello' 'hello'.padEnd(10); // => 'hello ' 'hello'.padEnd(10, '1234'); // => 'hello12341' ``` * `Object#__(define|lookup)[GS]etter__`, [annex B ES2017](https://github.com/tc39/ecma262/pull/381), but we haven't special namespace for that - modules [`es7.object.define-setter`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.define-setter.js), [`es7.object.define-getter`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.define-getter.js), [`es7.object.lookup-setter`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.lookup-setter.js) and [`es7.object.lookup-getter`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.object.lookup-getter.js). ```js Object #__defineSetter__(key, fn) -> void #__defineGetter__(key, fn) -> void #__lookupSetter__(key) -> fn | void #__lookupGetter__(key) -> fn | void ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/object/define-getter core-js(/library)/fn/object/define-setter core-js(/library)/fn/object/lookup-getter core-js(/library)/fn/object/lookup-setter ``` #### Stage 3 proposals [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/stage/3 ``` * `global` [proposal](https://github.com/tc39/proposal-global) - modules [`es7.global`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.global.js) and [`es7.system.global`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.system.global.js) (obsolete) ```js global -> object System .global -> object (obsolete) ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/global core-js(/library)/fn/system/global (obsolete) ``` [*Examples*](http://goo.gl/gEqMl7): ```js global.Array === Array; // => true ``` * `Promise#finally` [proposal](https://github.com/tc39/proposal-promise-finally) - module [`es7.promise.finally`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.promise.finally.js) ```js Promise #finally(onFinally()) -> promise ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/promise/finally ``` [*Examples*](https://goo.gl/AhyBbJ): ```js Promise.resolve(42).finally(() => console.log('You will see it anyway')); Promise.reject(42).finally(() => console.log('You will see it anyway')); #### Stage 2 proposals [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/stage/2 ``` * `String#trimLeft`, `String#trimRight` / `String#trimStart`, `String#trimEnd` [proposal](https://github.com/sebmarkbage/ecmascript-string-left-right-trim) - modules [`es7.string.trim-left`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.string.trim-right.js), [`es7.string.trim-right`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.string.trim-right.js) ```js String #trimLeft() -> string #trimRight() -> string #trimStart() -> string #trimEnd() -> string ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/string/trim-start core-js(/library)/fn/string/trim-end core-js(/library)/fn/string/trim-left core-js(/library)/fn/string/trim-right core-js(/library)/fn/string/virtual/trim-start core-js(/library)/fn/string/virtual/trim-end core-js(/library)/fn/string/virtual/trim-left core-js(/library)/fn/string/virtual/trim-right ``` [*Examples*](http://goo.gl/Er5lMJ): ```js ' hello '.trimLeft(); // => 'hello ' ' hello '.trimRight(); // => ' hello' ``` ``` * `Symbol.asyncIterator` for [async iteration proposal](https://github.com/tc39/proposal-async-iteration) - module [`es7.symbol.async-iterator`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.symbol.async-iterator.js) ```js Symbol .asyncIterator -> @@asyncIterator ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/symbol/async-iterator ``` #### Stage 1 proposals [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/stage/1 ``` * `Promise.try` [proposal](https://github.com/tc39/proposal-promise-try) - module [`es7.promise.try`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.promise.try.js) ```js Promise .try(function()) -> promise ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/promise/try ``` [*Examples*](https://goo.gl/k5GGRo): ```js Promise.try(() => 42).then(it => console.log(`Promise, resolved as ${it}`)); Promise.try(() => { throw 42; }).catch(it => console.log(`Promise, rejected as ${it}`)); ``` * `Array#flatten` and `Array#flatMap` [proposal](https://tc39.github.io/proposal-flatMap) - modules [`es7.array.flatten`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.array.flatten.js) and [`es7.array.flat-map`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.array.flat-map.js) ```js Array #flatten(depthArg = 1) -> array #flatMap(fn(val, key, @), that) -> array ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/array/flatten core-js(/library)/fn/array/flat-map core-js(/library)/fn/array/virtual/flatten core-js(/library)/fn/array/virtual/flat-map ``` [*Examples*](https://goo.gl/jTXsZi): ```js [1, [2, 3], [4, 5]].flatten(); // => [1, 2, 3, 4, 5] [1, [2, [3, [4]]], 5].flatten(); // => [1, 2, [3, [4]], 5] [1, [2, [3, [4]]], 5].flatten(3); // => [1, 2, 3, 4, 5] [{a: 1, b: 2}, {a: 3, b: 4}, {a: 5, b: 6}].flatMap(it => [it.a, it.b]); // => [1, 2, 3, 4, 5, 6] ``` * `.of` and `.from` methods on collection constructors [proposal](https://github.com/tc39/proposal-setmap-offrom) - modules [`es7.set.of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.set.of.js), [`es7.set.from`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.set.from.js), [`es7.map.of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.map.of.js), [`es7.map.from`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.map.from.js), [`es7.weak-set.of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.weak-set.of.js), [`es7.weak-set.from`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.weak-set.from.js), [`es7.weak-map.of`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.weak-map.of.js), [`es7.weak-map.from`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.weak-map.from.js) ```js Set .of(...args) -> set .from(iterable, mapFn(val, index)?, that?) -> set Map .of(...args) -> map .from(iterable, mapFn(val, index)?, that?) -> map WeakSet .of(...args) -> weakset .from(iterable, mapFn(val, index)?, that?) -> weakset WeakMap .of(...args) -> weakmap .from(iterable, mapFn(val, index)?, that?) -> weakmap ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/set/of core-js(/library)/fn/set/from core-js(/library)/fn/map/of core-js(/library)/fn/map/from core-js(/library)/fn/weak-set/of core-js(/library)/fn/weak-set/from core-js(/library)/fn/weak-map/of core-js(/library)/fn/weak-map/from ``` [*Examples*](https://goo.gl/mSC7eU): ```js Set.of(1, 2, 3, 2, 1); // => Set {1, 2, 3} Map.from([[1, 2], [3, 4]], ([key, val]) => [key ** 2, val ** 2]); // => Map {1: 4, 9: 16} ``` * `String#matchAll` [proposal](https://github.com/tc39/String.prototype.matchAll) - module [`es7.string.match-all`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.string.match-all.js) ```js String #matchAll(regexp) -> iterator ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/string/match-all core-js(/library)/fn/string/virtual/match-all ``` [*Examples*](http://goo.gl/6kp9EB): ```js for(let [_, d, D] of '1111a2b3cccc'.matchAll(/(\d)(\D)/)){ console.log(d, D); // => 1 a, 2 b, 3 c } ``` * `Observable` [proposal](https://github.com/zenparsing/es-observable) - modules [`es7.observable`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.observable.js) and [`es7.symbol.observable`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.symbol.observable.js) ```js new Observable(fn) -> observable #subscribe(observer) -> subscription #forEach(fn) -> promise #@@observable() -> @ .of(...items) -> observable .from(observable | iterable) -> observable .@@species -> @ Symbol .observable -> @@observable ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/observable core-js(/library)/fn/symbol/observable ``` [*Examples*](http://goo.gl/1LDywi): ```js new Observable(observer => { observer.next('hello'); observer.next('world'); observer.complete(); }).forEach(it => console.log(it)) .then(_ => console.log('!')); ``` * `Math.{clamp, DEG_PER_RAD, degrees, fscale, rad-per-deg, radians, scale}` [proposal](https://github.com/rwaldron/proposal-math-extensions) - modules [`es7.math.clamp`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.clamp.js), [`es7.math.DEG_PER_RAD`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.DEG_PER_RAD.js), [`es7.math.degrees`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.degrees.js), [`es7.math.fscale`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.fscale.js), [`es7.math.RAD_PER_DEG`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.RAD_PER_DEG.js), [`es7.math.radians`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.radians.js) and [`es7.math.scale`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.scale.js) ```js Math .DEG_PER_RAD -> number .RAD_PER_DEG -> number .clamp(x, lower, upper) -> number .degrees(radians) -> number .fscale(x, inLow, inHigh, outLow, outHigh) -> number .radians(degrees) -> number .scale(x, inLow, inHigh, outLow, outHigh) -> number ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/math/clamp core-js(/library)/fn/math/deg-per-rad core-js(/library)/fn/math/degrees core-js(/library)/fn/math/fscale core-js(/library)/fn/math/rad-per-deg core-js(/library)/fn/math/radians core-js(/library)/fn/math/scale ``` * `Math.signbit` [proposal](http://jfbastien.github.io/papers/Math.signbit.html) - module [`es7.math.signbit`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.signbit.js) ```js Math .signbit(x) -> bool ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/math/signbit ``` [*Examples*](http://es6.zloirock.ru/): ```js Math.signbit(NaN); // => NaN Math.signbit(1); // => true Math.signbit(-1); // => false Math.signbit(0); // => true Math.signbit(-0); // => false ``` #### Stage 0 proposals [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/stage/0 ``` * `String#at` [proposal](https://github.com/mathiasbynens/String.prototype.at) - module [`es7.string.at`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.string.at.js) ```js String #at(index) -> string ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/string/at core-js(/library)/fn/string/virtual/at ``` [*Examples*](http://goo.gl/XluXI8): ```js 'a𠮷b'.at(1); // => '𠮷' 'a𠮷b'.at(1).length; // => 2 ``` * `Map#toJSON`, `Set#toJSON` [proposal](https://github.com/DavidBruant/Map-Set.prototype.toJSON) - modules [`es7.map.to-json`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.map.to-json.js), [`es7.set.to-json`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.set.to-json.js) (rejected and will be removed from `core-js@3`) ```js Map #toJSON() -> array (rejected and will be removed from core-js@3) Set #toJSON() -> array (rejected and will be removed from core-js@3) ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/map core-js(/library)/fn/set ``` * `Error.isError` [proposal](https://github.com/ljharb/proposal-is-error) - module [`es7.error.is-error`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.error.is-error.js) (withdrawn and will be removed from `core-js@3`) ```js Error .isError(it) -> bool (withdrawn and will be removed from core-js@3) ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/error/is-error ``` * `Math.{iaddh, isubh, imulh, umulh}` [proposal](https://gist.github.com/BrendanEich/4294d5c212a6d2254703) - modules [`es7.math.iaddh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.iaddh.js), [`es7.math.isubh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.isubh.js), [`es7.math.imulh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.imulh.js) and [`es7.math.umulh`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.math.umulh.js) ```js Math .iaddh(lo0, hi0, lo1, hi1) -> int32 .isubh(lo0, hi0, lo1, hi1) -> int32 .imulh(a, b) -> int32 .umulh(a, b) -> uint32 ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/math/iaddh core-js(/library)/fn/math/isubh core-js(/library)/fn/math/imulh core-js(/library)/fn/math/umulh ``` * `global.asap`, [TC39 discussion](https://github.com/rwaldron/tc39-notes/blob/master/es6/2014-09/sept-25.md#510-globalasap-for-enqueuing-a-microtask), module [`es7.asap`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.asap.js) ```js asap(fn) -> void ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/asap ``` [*Examples*](http://goo.gl/tx3SRK): ```js asap(() => console.log('called as microtask')); ``` #### Pre-stage 0 proposals [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/stage/pre ``` * `Reflect` metadata [proposal](https://github.com/jonathandturner/decorators/blob/master/specs/metadata.md) - modules [`es7.reflect.define-metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.define-metadata.js), [`es7.reflect.delete-metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.delete-metadata.js), [`es7.reflect.get-metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.get-metadata.js), [`es7.reflect.get-metadata-keys`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.get-metadata-keys.js), [`es7.reflect.get-own-metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.get-own-metadata.js), [`es7.reflect.get-own-metadata-keys`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.get-own-metadata-keys.js), [`es7.reflect.has-metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.has-metadata.js), [`es7.reflect.has-own-metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.has-own-metadata.js) and [`es7.reflect.metadata`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/es7.reflect.metadata.js). ```js Reflect .defineMetadata(metadataKey, metadataValue, target, propertyKey?) -> void .getMetadata(metadataKey, target, propertyKey?) -> var .getOwnMetadata(metadataKey, target, propertyKey?) -> var .hasMetadata(metadataKey, target, propertyKey?) -> bool .hasOwnMetadata(metadataKey, target, propertyKey?) -> bool .deleteMetadata(metadataKey, target, propertyKey?) -> bool .getMetadataKeys(target, propertyKey?) -> array .getOwnMetadataKeys(target, propertyKey?) -> array .metadata(metadataKey, metadataValue) -> decorator(target, targetKey?) -> void ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/reflect/define-metadata core-js(/library)/fn/reflect/delete-metadata core-js(/library)/fn/reflect/get-metadata core-js(/library)/fn/reflect/get-metadata-keys core-js(/library)/fn/reflect/get-own-metadata core-js(/library)/fn/reflect/get-own-metadata-keys core-js(/library)/fn/reflect/has-metadata core-js(/library)/fn/reflect/has-own-metadata core-js(/library)/fn/reflect/metadata ``` [*Examples*](http://goo.gl/KCo3PS): ```js var O = {}; Reflect.defineMetadata('foo', 'bar', O); Reflect.ownKeys(O); // => [] Reflect.getOwnMetadataKeys(O); // => ['foo'] Reflect.getOwnMetadata('foo', O); // => 'bar' ``` ### Web standards [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/web ``` #### setTimeout / setInterval Module [`web.timers`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/web.timers.js). Additional arguments fix for IE9-. ```js setTimeout(fn(...args), time, ...args) -> id setInterval(fn(...args), time, ...args) -> id ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/web/timers core-js(/library)/fn/set-timeout core-js(/library)/fn/set-interval ``` ```js // Before: setTimeout(log.bind(null, 42), 1000); // After: setTimeout(log, 1000, 42); ``` #### setImmediate Module [`web.immediate`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/web.immediate.js). [`setImmediate` proposal](https://developer.mozilla.org/en-US/docs/Web/API/Window.setImmediate) polyfill. ```js setImmediate(fn(...args), ...args) -> id clearImmediate(id) -> void ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/web/immediate core-js(/library)/fn/set-immediate core-js(/library)/fn/clear-immediate ``` [*Examples*](http://goo.gl/6nXGrx): ```js setImmediate(function(arg1, arg2){ console.log(arg1, arg2); // => Message will be displayed with minimum delay }, 'Message will be displayed', 'with minimum delay'); clearImmediate(setImmediate(function(){ console.log('Message will not be displayed'); })); ``` #### Iterable DOM collections Some DOM collections should have [iterable interface](https://heycam.github.io/webidl/#idl-iterable) or should be [inherited from `Array`](https://heycam.github.io/webidl/#LegacyArrayClass). That mean they should have `keys`, `values`, `entries` and `@@iterator` methods for iteration. So add them. Module [`web.dom.iterable`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/web.dom.iterable.js): ```js { CSSRuleList, CSSStyleDeclaration, CSSValueList, ClientRectList, DOMRectList, DOMStringList, DOMTokenList, DataTransferItemList, FileList, HTMLAllCollection, HTMLCollection, HTMLFormElement, HTMLSelectElement, MediaList, MimeTypeArray, NamedNodeMap, NodeList, PaintRequestList, Plugin, PluginArray, SVGLengthList, SVGNumberList, SVGPathSegList, SVGPointList, SVGStringList, SVGTransformList, SourceBufferList, StyleSheetList, TextTrackCueList, TextTrackList, TouchList } #@@iterator() -> iterator (values) { DOMTokenList, NodeList } #values() -> iterator #keys() -> iterator #entries() -> iterator ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/web/dom-collections core-js(/library)/fn/dom-collections/iterator ``` [*Examples*](http://goo.gl/lfXVFl): ```js for(var {id} of document.querySelectorAll('*')){ if(id)console.log(id); } for(var [index, {id}] of document.querySelectorAll('*').entries()){ if(id)console.log(index, id); } ``` ### Non-standard [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/core ``` #### Object Modules [`core.object.is-object`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.object.is-object.js), [`core.object.classof`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.object.classof.js), [`core.object.define`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.object.define.js), [`core.object.make`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.object.make.js). ```js Object .isObject(var) -> bool .classof(var) -> string .define(target, mixin) -> target .make(proto | null, mixin?) -> object ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/core/object core-js(/library)/fn/object/is-object core-js(/library)/fn/object/define core-js(/library)/fn/object/make ``` Object classify [*examples*](http://goo.gl/YZQmGo): ```js Object.isObject({}); // => true Object.isObject(isNaN); // => true Object.isObject(null); // => false var classof = Object.classof; classof(null); // => 'Null' classof(undefined); // => 'Undefined' classof(1); // => 'Number' classof(true); // => 'Boolean' classof('string'); // => 'String' classof(Symbol()); // => 'Symbol' classof(new Number(1)); // => 'Number' classof(new Boolean(true)); // => 'Boolean' classof(new String('string')); // => 'String' var fn = function(){} , list = (function(){return arguments})(1, 2, 3); classof({}); // => 'Object' classof(fn); // => 'Function' classof([]); // => 'Array' classof(list); // => 'Arguments' classof(/./); // => 'RegExp' classof(new TypeError); // => 'Error' classof(new Set); // => 'Set' classof(new Map); // => 'Map' classof(new WeakSet); // => 'WeakSet' classof(new WeakMap); // => 'WeakMap' classof(new Promise(fn)); // => 'Promise' classof([].values()); // => 'Array Iterator' classof(new Set().values()); // => 'Set Iterator' classof(new Map().values()); // => 'Map Iterator' classof(Math); // => 'Math' classof(JSON); // => 'JSON' function Example(){} Example.prototype[Symbol.toStringTag] = 'Example'; classof(new Example); // => 'Example' ``` `Object.define` and `Object.make` [*examples*](http://goo.gl/rtpD5Z): ```js // Before: Object.defineProperty(target, 'c', { enumerable: true, configurable: true, get: function(){ return this.a + this.b; } }); // After: Object.define(target, { get c(){ return this.a + this.b; } }); // Shallow object cloning with prototype and descriptors: var copy = Object.make(Object.getPrototypeOf(src), src); // Simple inheritance: function Vector2D(x, y){ this.x = x; this.y = y; } Object.define(Vector2D.prototype, { get xy(){ return Math.hypot(this.x, this.y); } }); function Vector3D(x, y, z){ Vector2D.apply(this, arguments); this.z = z; } Vector3D.prototype = Object.make(Vector2D.prototype, { constructor: Vector3D, get xyz(){ return Math.hypot(this.x, this.y, this.z); } }); var vector = new Vector3D(9, 12, 20); console.log(vector.xy); // => 15 console.log(vector.xyz); // => 25 vector.y++; console.log(vector.xy); // => 15.811388300841896 console.log(vector.xyz); // => 25.495097567963924 ``` #### Dict Module [`core.dict`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.dict.js). Based on [TC39 discuss](https://github.com/rwaldron/tc39-notes/blob/master/es6/2012-11/nov-29.md#collection-apis-review) / [strawman](http://wiki.ecmascript.org/doku.php?id=harmony:modules_standard#dictionaries). ```js [new] Dict(iterable (entries) | object ?) -> dict .isDict(var) -> bool .values(object) -> iterator .keys(object) -> iterator .entries(object) -> iterator (entries) .has(object, key) -> bool .get(object, key) -> val .set(object, key, value) -> object .forEach(object, fn(val, key, @), that) -> void .map(object, fn(val, key, @), that) -> new @ .mapPairs(object, fn(val, key, @), that) -> new @ .filter(object, fn(val, key, @), that) -> new @ .some(object, fn(val, key, @), that) -> bool .every(object, fn(val, key, @), that) -> bool .find(object, fn(val, key, @), that) -> val .findKey(object, fn(val, key, @), that) -> key .keyOf(object, var) -> key .includes(object, var) -> bool .reduce(object, fn(memo, val, key, @), memo?) -> var ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/core/dict core-js(/library)/fn/dict ``` `Dict` create object without prototype from iterable or simple object. [*Examples*](http://goo.gl/pnp8Vr): ```js var map = new Map([['a', 1], ['b', 2], ['c', 3]]); Dict(); // => {__proto__: null} Dict({a: 1, b: 2, c: 3}); // => {__proto__: null, a: 1, b: 2, c: 3} Dict(map); // => {__proto__: null, a: 1, b: 2, c: 3} Dict([1, 2, 3].entries()); // => {__proto__: null, 0: 1, 1: 2, 2: 3} var dict = Dict({a: 42}); dict instanceof Object; // => false dict.a; // => 42 dict.toString; // => undefined 'a' in dict; // => true 'hasOwnProperty' in dict; // => false Dict.isDict({}); // => false Dict.isDict(Dict()); // => true ``` `Dict.keys`, `Dict.values` and `Dict.entries` returns iterators for objects. [*Examples*](http://goo.gl/xAvECH): ```js var dict = {a: 1, b: 2, c: 3}; for(var key of Dict.keys(dict))console.log(key); // => 'a', 'b', 'c' for(var val of Dict.values(dict))console.log(val); // => 1, 2, 3 for(var [key, val] of Dict.entries(dict)){ console.log(key); // => 'a', 'b', 'c' console.log(val); // => 1, 2, 3 } new Map(Dict.entries(dict)); // => Map {a: 1, b: 2, c: 3} ``` Basic dict operations for objects with prototype [*examples*](http://goo.gl/B28UnG): ```js 'q' in {q: 1}; // => true 'toString' in {}; // => true Dict.has({q: 1}, 'q'); // => true Dict.has({}, 'toString'); // => false ({q: 1})['q']; // => 1 ({}).toString; // => function toString(){ [native code] } Dict.get({q: 1}, 'q'); // => 1 Dict.get({}, 'toString'); // => undefined var O = {}; O['q'] = 1; O['q']; // => 1 O['__proto__'] = {w: 2}; O['__proto__']; // => {w: 2} O['w']; // => 2 var O = {}; Dict.set(O, 'q', 1); O['q']; // => 1 Dict.set(O, '__proto__', {w: 2}); O['__proto__']; // => {w: 2} O['w']; // => undefined ``` Other methods of `Dict` module are static equivalents of `Array.prototype` methods for dictionaries. [*Examples*](http://goo.gl/xFi1RH): ```js var dict = {a: 1, b: 2, c: 3}; Dict.forEach(dict, console.log, console); // => 1, 'a', {a: 1, b: 2, c: 3} // => 2, 'b', {a: 1, b: 2, c: 3} // => 3, 'c', {a: 1, b: 2, c: 3} Dict.map(dict, function(it){ return it * it; }); // => {a: 1, b: 4, c: 9} Dict.mapPairs(dict, function(val, key){ if(key != 'b')return [key + key, val * val]; }); // => {aa: 1, cc: 9} Dict.filter(dict, function(it){ return it % 2; }); // => {a: 1, c: 3} Dict.some(dict, function(it){ return it === 2; }); // => true Dict.every(dict, function(it){ return it === 2; }); // => false Dict.find(dict, function(it){ return it > 2; }); // => 3 Dict.find(dict, function(it){ return it > 4; }); // => undefined Dict.findKey(dict, function(it){ return it > 2; }); // => 'c' Dict.findKey(dict, function(it){ return it > 4; }); // => undefined Dict.keyOf(dict, 2); // => 'b' Dict.keyOf(dict, 4); // => undefined Dict.includes(dict, 2); // => true Dict.includes(dict, 4); // => false Dict.reduce(dict, function(memo, it){ return memo + it; }); // => 6 Dict.reduce(dict, function(memo, it){ return memo + it; }, ''); // => '123' ``` #### Partial application Module [`core.function.part`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.function.part.js). ```js Function #part(...args | _) -> fn(...args) ``` [*CommonJS entry points:*](#commonjs) ```js core-js/core/function core-js(/library)/fn/function/part core-js(/library)/fn/function/virtual/part core-js(/library)/fn/_ ``` `Function#part` partial apply function without `this` binding. Uses global variable `_` (`core._` for builds without global namespace pollution) as placeholder and not conflict with `Underscore` / `LoDash`. [*Examples*](http://goo.gl/p9ZJ8K): ```js var fn1 = log.part(1, 2); fn1(3, 4); // => 1, 2, 3, 4 var fn2 = log.part(_, 2, _, 4); fn2(1, 3); // => 1, 2, 3, 4 var fn3 = log.part(1, _, _, 4); fn3(2, 3); // => 1, 2, 3, 4 fn2(1, 3, 5); // => 1, 2, 3, 4, 5 fn2(1); // => 1, 2, undefined, 4 ``` #### Number Iterator Module [`core.number.iterator`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.number.iterator.js). ```js Number #@@iterator() -> iterator ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/core/number core-js(/library)/fn/number/iterator core-js(/library)/fn/number/virtual/iterator ``` [*Examples*](http://goo.gl/o45pCN): ```js for(var i of 3)console.log(i); // => 0, 1, 2 [...10]; // => [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] Array.from(10, Math.random); // => [0.9817775336559862, 0.02720663254149258, ...] Array.from(10, function(it){ return this + it * it; }, .42); // => [0.42, 1.42, 4.42, 9.42, 16.42, 25.42, 36.42, 49.42, 64.42, 81.42] ``` #### Escaping strings Modules [`core.regexp.escape`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.regexp.escape.js), [`core.string.escape-html`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.string.escape-html.js) and [`core.string.unescape-html`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.string.unescape-html.js). ```js RegExp .escape(str) -> str String #escapeHTML() -> str #unescapeHTML() -> str ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/core/regexp core-js(/library)/core/string core-js(/library)/fn/regexp/escape core-js(/library)/fn/string/escape-html core-js(/library)/fn/string/unescape-html core-js(/library)/fn/string/virtual/escape-html core-js(/library)/fn/string/virtual/unescape-html ``` [*Examples*](http://goo.gl/6bOvsQ): ```js RegExp.escape('Hello, []{}()*+?.\\^$|!'); // => 'Hello, \[\]\{\}\(\)\*\+\?\.\\\^\$\|!' ''.escapeHTML(); // => '<script>doSomething();</script>' '<script>doSomething();</script>'.unescapeHTML(); // => '' ``` #### delay Module [`core.delay`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.delay.js). [Promise](#ecmascript-6-promise)-returning delay function, [esdiscuss](https://esdiscuss.org/topic/promise-returning-delay-function). ```js delay(ms) -> promise ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/core/delay core-js(/library)/fn/delay ``` [*Examples*](http://goo.gl/lbucba): ```js delay(1e3).then(() => console.log('after 1 sec')); (async () => { await delay(3e3); console.log('after 3 sec'); while(await delay(3e3))console.log('each 3 sec'); })(); ``` #### Helpers for iterators Modules [`core.is-iterable`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.is-iterable.js), [`core.get-iterator`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.get-iterator.js), [`core.get-iterator-method`](https://github.com/zloirock/core-js/blob/v2.6.9/modules/core.get-iterator-method.js) - helpers for check iterability / get iterator in the `library` version or, for example, for `arguments` object: ```js core .isIterable(var) -> bool .getIterator(iterable) -> iterator .getIteratorMethod(var) -> function | undefined ``` [*CommonJS entry points:*](#commonjs) ```js core-js(/library)/fn/is-iterable core-js(/library)/fn/get-iterator core-js(/library)/fn/get-iterator-method ``` [*Examples*](http://goo.gl/SXsM6D): ```js var list = (function(){ return arguments; })(1, 2, 3); console.log(core.isIterable(list)); // true; var iter = core.getIterator(list); console.log(iter.next().value); // 1 console.log(iter.next().value); // 2 console.log(iter.next().value); // 3 console.log(iter.next().value); // undefined core.getIterator({}); // TypeError: [object Object] is not iterable! var iterFn = core.getIteratorMethod(list); console.log(typeof iterFn); // 'function' var iter = iterFn.call(list); console.log(iter.next().value); // 1 console.log(iter.next().value); // 2 console.log(iter.next().value); // 3 console.log(iter.next().value); // undefined console.log(core.getIteratorMethod({})); // undefined ``` ## Missing polyfills - ES5 `JSON` is missing now only in IE7- and never will it be added to `core-js`, if you need it in these old browsers, many implementations are available, for example, [json3](https://github.com/bestiejs/json3). - ES6 `String#normalize` is not a very useful feature, but this polyfill will be very large. If you need it, you can use [unorm](https://github.com/walling/unorm/). - ES6 `Proxy` can't be polyfilled, but for Node.js / Chromium with additional flags you can try [harmony-reflect](https://github.com/tvcutsem/harmony-reflect) for adapt old style `Proxy` API to final ES6 version. - ES6 logic for `@@isConcatSpreadable` and `@@species` (in most places) can be polyfilled without problems, but it will cause a serious slowdown in popular cases in some engines. It will be polyfilled when it will be implemented in modern engines. - ES7 `SIMD`. `core-js` doesn't add polyfill of this feature because of large size and some other reasons. You can use [this polyfill](https://github.com/tc39/ecmascript_simd/blob/master/src/ecmascript_simd.js). - `window.fetch` is not a cross-platform feature, in some environments it makes no sense. For this reason, I don't think it should be in `core-js`. Looking at a large number of requests it *may be* added in the future. Now you can use, for example, [this polyfill](https://github.com/github/fetch). - ECMA-402 `Intl` is missed because of size. You can use [this polyfill](https://github.com/andyearnshaw/Intl.js/).