core-js-ie8

core-js

Modular standard library for JavaScript. Includes polyfills for ECMAScript 5, ECMAScript 6: promises, symbols, collections, iterators, typed arrays, ECMAScript 7+ proposals, setImmediate, etc. Some additional features such as dictionaries or extended partial application. You can require only needed features or use it without global namespace pollution.

Example:

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:

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

• Usage
  • Basic
  • CommonJS
  • Custom build
• Supported engines
• Features
  • ECMAScript 5
  • ECMAScript 6
    • ECMAScript 6: Object
    • ECMAScript 6: Function
    • ECMAScript 6: Array
    • ECMAScript 6: String
    • ECMAScript 6: RegExp
    • ECMAScript 6: Number
    • ECMAScript 6: Math
    • ECMAScript 6: Date
    • ECMAScript 6: Promise
    • ECMAScript 6: Symbol
    • ECMAScript 6: Collections
    • ECMAScript 6: Typed Arrays
    • ECMAScript 6: Reflect
  • ECMAScript 7+ proposals
  • Web standards
    • setTimeout / setInterval
    • setImmediate
    • Iterable DOM collections
  • Non-standard
    • Object
    • Dict
    • Partial application
    • Number Iterator
    • Escaping strings
    • delay
    • Helpers for iterators
• Missing polyfills
• Changelog

Usage

Basic

npm i core-js
bower install core.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: Includes all features, standard and non-standard.
• as a library: Like "default", but does not pollute the global namespace (see 2nd example at the top).
• shim only: 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.

require('core-js/es5'); // if you need support IE8-
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 core      = require('core-js/library/es5'); // if you need support IE8-
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, excluding features from es5 module (this module requires completely in ES3 environment before all other modules).

Available namespaces: for example, core-js/es6/array (core-js/library/es6/array) contains all ES6 Array features, 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. Special for that, available /virtual/ entry points. Example:

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, es6 contains all modules whose names start with es6.

Custom build (from external scripts)

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:

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
}).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
• 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:

core-js(/library)       <- all features
core-js(/library)/shim  <- only polyfills

ECMAScript 5

Module es5, nothing new - without examples.

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
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
Function
  #bind(object, ...args) -> boundFn(...args)
Date
  .now() -> int
  #toISOString() -> string

Some features moved to another modules / namespaces, but available as part of es5 namespace too:

Object
  .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-
String
  #trim() -> str

CommonJS entry points:

core-js(/library)/es5

ECMAScript 6

CommonJS entry points:

core-js(/library)/es6

ECMAScript 6: Object

Modules es6.object.assign, es6.object.is, es6.object.set-prototype-of and es6.object.to-string.

In ES6 most Object static methods should work with primitives. Modules es6.object.freeze, es6.object.seal, es6.object.prevent-extensions, es6.object.is-frozen, es6.object.is-sealed, es6.object.is-extensible, es6.object.get-own-property-descriptor, es6.object.get-prototype-of, es6.object.keys, es6.object.get-own-property-names.

Object
  .assign(target, ...src) -> target
  .is(a, b) -> bool
  .setPrototypeOf(target, proto | null) -> target (required __proto__ - IE11+)
  .freeze(var) -> var
  .seal(var) -> var
  .preventExtensions(var) -> var
  .isFrozen(var) -> bool
  .isSealed(var) -> bool
  .isExtensible(var) -> bool
  .getOwnPropertyDescriptor(var, key) -> desc | undefined
  .getPrototypeOf(var) -> object | null
  .keys(var) -> array
  .getOwnPropertyNames(var) -> array
  #toString() -> string, ES6 fix: @@toStringTag support

CommonJS entry points:

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/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(/library)/fn/object/get-own-property-descriptor
core-js(/library)/fn/object/get-prototype-of
core-js(/library)/fn/object/keys
core-js(/library)/fn/object/get-own-property-names
core-js/fn/object/to-string

Examples:

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 and es6.function.has-instance.

Function
  #name -> string (IE9+)
  #@@hasInstance(var) -> bool

CommonJS entry points:

core-js/es6/function
core-js/fn/function/name
core-js/fn/function/has-instance

Example:

(function foo(){}).name // => 'foo'

ECMAScript 6: Array

Modules es6.array.from, es6.array.of, es6.array.copy-within, es6.array.fill, es6.array.find, es6.array.find-index and es6.array.iterator.

Array
  .from(iterable | array-like, mapFn(val, index)?, that) -> array
  .of(...args) -> array
  #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
  #values() -> iterator
  #keys() -> iterator
  #entries() -> iterator
  #@@iterator() -> iterator (values)
  #@@unscopables -> object (cap)
Arguments
  #@@iterator() -> iterator (values, available only in core-js methods)

CommonJS entry points:

core-js(/library)/es6/array
core-js(/library)/fn/array/from
core-js(/library)/fn/array/of
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/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/iterator

Examples:

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, es6.string.raw, es6.string.iterator, es6.string.code-point-at, es6.string.ends-with, es6.string.includes, es6.string.repeat, es6.string.starts-with and es6.string.trim.

Annex B HTML methods. Ugly, but it's also the part of the spec. Modules es6.string.anchor, es6.string.big, es6.string.blink, es6.string.bold, es6.string.fixed, es6.string.fontcolor, es6.string.fontsize, es6.string.italics, es6.string.link, es6.string.small, es6.string.strike, es6.string.sub and es6.string.sup.

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:

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:

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();                     // => '<b>foo</b>'
'bar'.anchor('a"b');              // => '<a name="a&quot;b">bar</a>'
'baz'.link('http://example.com'); // => '<a href="http://example.com">baz</a>'

ECMAScript 6: RegExp

Modules es6.regexp.constructor and es6.regexp.flags.

Support well-known symbols @@match, @@replace, @@search and @@split, modules es6.regexp.match, es6.regexp.replace, es6.regexp.search and es6.regexp.split.

[new] RegExp(pattern, flags?) -> regexp, ES6 fix: can alter flags (IE9+)
  #flags -> str (IE9+)
  #@@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

CommonJS entry points:

core-js/es6/regexp
core-js/fn/regexp/constructor
core-js(/library)/fn/regexp/flags
core-js/fn/regexp/match
core-js/fn/regexp/replace
core-js/fn/regexp/search
core-js/fn/regexp/split

Examples:

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

ECMAScript 6: Number

Module es6.number.constructor. Number constructor support binary and octal literals, example:

Number('0b1010101'); // => 85
Number('0o7654321'); // => 2054353

Number: modules es6.number.epsilon, es6.number.is-finite, es6.number.is-integer, es6.number.is-nan, es6.number.is-safe-integer, es6.number.max-safe-integer, es6.number.min-safe-integer, es6.number.parse-float, es6.number.parse-int.

[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

CommonJS entry points:

core-js(/library)/es6/number
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/es6/number/constructor

ECMAScript 6: Math

Math: modules es6.math.acosh, es6.math.asinh, es6.math.atanh, es6.math.cbrt, es6.math.clz32, es6.math.cosh, es6.math.expm1, es6.math.fround, es6.math.hypot, es6.math.imul, es6.math.log10, es6.math.log1p, es6.math.log2, es6.math.sign, es6.math.sinh, es6.math.tanh, es6.math.trunc.

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:

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

Currently - only one little fix for Date#toString. Module es6.date.to-string:

Date
  #toString() -> str

CommonJS entry points:

core-js/es6/date
core-js/fn/date/to-string

Example:

new Date(NaN).toString(); // => 'Invalid Date'

ECMAScript 6: Promise

Module es6.promise.

new Promise(executor(resolve(var), reject(var))) -> promise
  #then(resolved(var), rejected(var)) -> promise
  #catch(rejected(var)) -> promise
  .resolve(var || promise) -> promise
  .reject(var) -> promise
  .all(iterable) -> promise
  .race(iterable) -> promise

CommonJS entry points:

core-js(/library)/es6/promise
core-js(/library)/fn/promise

Basic example:

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:

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:

Promise.all([
  'foo',
  sleepRandom(5),
  sleepRandom(15),
  sleepRandom(10)             // after 15 sec:
]).then(x => console.log(x)); // => ['foo', 956, 85, 382]

Promise.race example:

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 example:

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

core-js Promise supports (but not adds to native implementations) unhandled rejection tracking.

In Node.js, like in native implementation, available events unhandledRejection and rejectionHandled:

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:

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]

Warning: The problem here - we can't add it to native Promise implementations, but by idea core-js should use enough correct native implementation if it's available. Currently, most native implementations are buggy and core-js uses polyfill, but the situation will be changed. If someone wanna use this hook everywhere - he should delete window.Promise before inclusion core-js.

ECMAScript 6: Symbol

Module es6.symbol.

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.

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:

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:

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:

var symbol = Symbol.for('key');
symbol === Symbol.for('key'); // true
Symbol.keyFor(symbol);        // 'key'

Example with methods for getting own object keys:

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:

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.

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.

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:

core-js(/library)/es6/map
core-js(/library)/fn/map

Examples:

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.

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:

core-js(/library)/es6/set
core-js(/library)/fn/set

Examples:

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.

new WeakMap(iterable (entries) ?) -> weakmap
  #delete(key) -> bool
  #get(key) -> val
  #has(key) -> bool
  #set(key, val) -> @

CommonJS entry points:

core-js(/library)/es6/weak-map
core-js(/library)/fn/weak-map

Examples:

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.

new WeakSet(iterable?) -> weakset
  #add(key) -> @
  #delete(key) -> bool
  #has(key) -> bool

CommonJS entry points:

core-js(/library)/es6/weak-set
core-js(/library)/fn/weak-set

Examples:

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, es6.typed.data-view, es6.typed.int8-array, es6.typed.uint8-array, es6.typed.uint8-clamped-array, es6.typed.int16-array, es6.typed.uint16-array, es6.typed.int32-array, es6.typed.uint32-array, es6.typed.float32-array and es6.typed.float64-array.

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
  #includes(var, from?) -> bool
  #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:

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:

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, es6.reflect.construct, es6.reflect.define-property, es6.reflect.delete-property, es6.reflect.enumerate, es6.reflect.get, es6.reflect.get-own-property-descriptor, es6.reflect.get-prototype-of, es6.reflect.has, es6.reflect.is-extensible, es6.reflect.own-keys, es6.reflect.prevent-extensions, es6.reflect.set, es6.reflect.set-prototype-of.

Reflect
  .apply(target, thisArgument, argumentsList) -> var
  .construct(target, argumentsList, newTarget?) -> object
  .defineProperty(target, propertyKey, attributes) -> bool
  .deleteProperty(target, propertyKey) -> bool
  .enumerate(target) -> iterator
  .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:

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
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:

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.

CommonJS entry points:

core-js(/library)/es7
core-js(/library)/es7/array
core-js(/library)/es7/string
core-js(/library)/es7/map
core-js(/library)/es7/set
core-js(/library)/es7/math
core-js(/library)/es7/system
core-js(/library)/es7/error

core-js/stage/4 entry point contains only stage 4 proposals, core-js/stage/3 - stage 3 and stage 4, etc.

Stage 4:

• {Array, %TypedArray%}#includes proposal - module es7.array.includes, %TypedArray% version in modules from this section.

CommonJS entry points:

core-js(/library)/stage/4
core-js(/library)/fn/array/includes

Stage 3:

• Object.values, Object.entries proposal - modules es7.object.values, es7.object.entries
• String#padStart, String#padEnd proposal - modules es7.string.pad-left, es7.string.pad-right

CommonJS entry points:

core-js(/library)/stage/3
core-js(/library)/fn/object/values
core-js(/library)/fn/object/entries
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

Stage 2:

None.

CommonJS entry points:

core-js(/library)/stage/2

Stage 1:

• String#trimLeft, String#trimRight / String#trimStart, String#trimEnd proposal - modules es7.string.trim-left, es7.string.trim-right
• System.global proposal - module es7.system.global

CommonJS entry points:

core-js(/library)/stage/1
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
core-js(/library)/fn/system/global

Stage 0:

• String#at proposal - module es7.string.at
• Object.getOwnPropertyDescriptors proposal - module es7.object.get-own-property-descriptors
• Map#toJSON, Set#toJSON proposal - modules es7.map.to-json, es7.set.to-json
• Error.isError proposal - module es7.error.is-error
• Math.{iaddh, isubh, imulh, umulh} proposal - modules es7.math.iaddh, es7.math.isubh, es7.math.imulh and es7.math.umulh.

CommonJS entry points:

core-js(/library)/stage/0
core-js(/library)/fn/string/at
core-js(/library)/fn/string/virtual/at
core-js(/library)/fn/object/get-own-property-descriptors
core-js(/library)/fn/map
core-js(/library)/fn/set
core-js(/library)/fn/error/is-error
core-js(/library)/fn/math/iaddh
core-js(/library)/fn/math/isubh
core-js(/library)/fn/math/imulh
core-js(/library)/fn/math/umulh

Pre-stage 0 proposals:

None.

CommonJS entry points:

core-js(/library)/stage/pre

Array
  #includes(var, from?) -> bool
String
  #at(index) -> string
  #padStart(length, fillStr = ' ') -> string
  #padEnd(length, fillStr = ' ') -> string
  #trimLeft() -> string
  #trimRight() -> string
  #trimStart() -> string
  #trimEnd() -> string
Object
  .values(object) -> array
  .entries(object) -> array
  .getOwnPropertyDescriptors(object) -> object
RegExp
  .escape(str) -> str
Map
  #toJSON() -> array
Set
  #toJSON() -> array
System
  .global -> object
Error
  .isError(it) -> bool
Math
  .iaddh(lo0, hi0, lo1, hi1) -> int32
  .isubh(lo0, hi0, lo1, hi1) -> int32
  .imulh(a, b) -> int32
  .umulh(a, b) -> uint32

Examples:

[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
 
'a𠮷b'.at(1);        // => '𠮷'
'a𠮷b'.at(1).length; // => 2
 
'hello'.padStart(10);         // => '     hello'
'hello'.padStart(10, '1234'); // => '12341hello'
'hello'.padEnd(10);           // => 'hello     '
'hello'.padEnd(10, '1234');   // => 'hello12341'
 
'   hello   '.trimLeft();  // => 'hello   '
'   hello   '.trimRight(); // => '   hello'
 
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]]
 
// Shallow object cloning with prototype and descriptors:
var copy = Object.create(Object.getPrototypeOf(O), Object.getOwnPropertyDescriptors(O));
// Mixin:
Object.defineProperties(target, Object.getOwnPropertyDescriptors(source));
 
JSON.stringify(new Map([['a', 'b'], ['c', 'd']])); // => '[["a","b"],["c","d"]]'
JSON.stringify(new Set([1, 2, 3, 2, 1]));          // => '[1,2,3]'
 
System.global.Array === Array; // => true
 
Error.isError(new TypeError); // => true

Web standards

CommonJS entry points:

core-js(/library)/web

setTimeout / setInterval

Module web.timers. Additional arguments fix for IE9-.

setTimeout(fn(...args), time, ...args) -> id
setInterval(fn(...args), time, ...args) -> id

CommonJS entry points:

core-js(/library)/web/timers
core-js(/library)/fn/set-timeout
core-js(/library)/fn/set-interval

// Before:
setTimeout(log.bind(null, 42), 1000);
// After:
setTimeout(log, 1000, 42);

setImmediate

Module web.immediate. setImmediate proposal polyfill.

setImmediate(fn(...args), ...args) -> id
clearImmediate(id) -> void

CommonJS entry points:

core-js(/library)/web/immediate
core-js(/library)/fn/set-immediate
core-js(/library)/fn/clear-immediate

Examples:

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 or should be inherited from Array. That mean they should have keys, values, entries and @@iterator methods for iteration. So add them. Module web.dom.iterable:

{
  NodeList,
  DOMTokenList,
  MediaList,
  StyleSheetList,
  CSSRuleList
}
  #values()     -> iterator
  #keys()       -> iterator
  #entries()    -> iterator
  #@@iterator() -> iterator (values)

CommonJS entry points:

core-js(/library)/web/dom-collections
core-js(/library)/fn/dom-collections/iterator

Examples:

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:

core-js(/library)/core

Object

Modules core.object.is-object, core.object.classof, core.object.define, core.object.make.

Object
  .isObject(var) -> bool
  .classof(var) -> string
  .define(target, mixin) -> target
  .make(proto | null, mixin?) -> object

CommonJS entry points:

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:

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:

// 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. Based on TC39 discuss / strawman.

[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:

core-js(/library)/core/dict
core-js(/library)/fn/dict

Dict create object without prototype from iterable or simple object.

Examples:

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:

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:

'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 equialents of Array.prototype methods for dictionaries.

Examples:

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.

Function
  #part(...args | _) -> fn(...args)

CommonJS entry points:

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:

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.

Number
  #@@iterator() -> iterator

CommonJS entry points:

core-js(/library)/core/number
core-js(/library)/fn/number/iterator
core-js(/library)/fn/number/virtual/iterator

Examples:

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, core.string.escape-html and core.string.unescape-html.

RegExp
  .escape(str) -> str
String
  #escapeHTML() -> str
  #unescapeHTML() -> str

CommonJS entry points:

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:

RegExp.escape('Hello, []{}()*+?.\\^$|!'); // => 'Hello, \[\]\{\}\(\)\*\+\?\.\\\^\$\|!'
 
'<script>doSomething();</script>'.escapeHTML(); // => '&lt;script&gt;doSomething();&lt;/script&gt;'
'&lt;script&gt;doSomething();&lt;/script&gt;'.unescapeHTML(); // => '<script>doSomething();</script>'

delay

Module core.delay. Promise-returning delay function, esdiscuss.

delay(ms) -> promise

CommonJS entry points:

core-js(/library)/core/delay
core-js(/library)/fn/delay

Examples:

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, core.get-iterator, core.get-iterator-method - helpers for check iterability / get iterator in the library version or, for example, for arguments object:

core
  .isIterable(var) -> bool
  .getIterator(iterable) -> iterator
  .getIteratorMethod(var) -> function | undefined

CommonJS entry points:

core-js(/library)/fn/is-iterable
core-js(/library)/fn/get-iterator
core-js(/library)/fn/get-iterator-method

Examples:

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.
• ES6 String#normalize is not a very useful feature, but this polyfill will be very large. If you need it, you can use unorm.
• ES6 Proxy can't be polyfilled, but for Node.js / Chromium with additional flags you can try 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.
• window.fetch is not a cross-platform feature, in some environments it make no sense. For this reason, I don't think it should be in core-js. Looking at a large number of requests it maybe added in the future. Now you can use, for example, this polyfill.