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)]
Symbol polyfill:Symbol returns object.Symbol.for and Symbol.keyFor can't be shimmed cross-realm.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
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.localStorage).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).
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)
core-js(/library)/es6/map
core-js(/library)/fn/map
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
}
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)
core-js(/library)/es6/set
core-js(/library)/fn/set
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
}
Module es6.weak-map.
new WeakMap(iterable (entries) ?) -> weakmap
#delete(key) -> bool
#get(key) -> val
#has(key) -> bool
#set(key, val) -> @
core-js(/library)/es6/weak-map
core-js(/library)/fn/weak-map
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'
Module es6.weak-set.
new WeakSet(iterable?) -> weakset
#add(key) -> @
#delete(key) -> bool
#has(key) -> bool
core-js(/library)/es6/weak-set
core-js(/library)/fn/weak-set
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
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
#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
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
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
}
Uint8ClampedArray in IE10 and early IE11), all modern engines have native typed arrays and requires only constructors fixes and methods.library version we can't pollute native prototypes, so prototype methods available as constructors static.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 (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+)
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
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
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.
core-js(/library)/stage/4
{Array, %TypedArray%}#includes proposal - module es7.array.includes, %TypedArray% version in modules from this section.
js
Array
#includes(var, from?) -> bool
{
Int8Array,
Uint8Array,
Uint8ClampedArray,
Int16Array,
Uint16Array,
Int32Array,
Uint32Array,
Float32Array,
Float64Array
}
#includes(var, from?) -> bool
CommonJS entry points:
js
core-js(/library)/fn/array/includes
Examples:
```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/v2.5.5/modules/es7.object.values.js), [`es7.object.entries`](https://github.com/zloirock/core-js/blob/v2.5.5/modules/es7.object.entries.js)
```js
Object
.values(object) -> array
.entries(object) -> array
core-js(/library)/fn/object/values
core-js(/library)/fn/object/entries
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 - module es7.object.get-own-property-descriptors
js
Object
.getOwnPropertyDescriptors(object) -> object
CommonJS entry points:
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 - modules es7.string.pad-start, es7.string.pad-end
js
String
#padStart(length, fillStr = ' ') -> string
#padEnd(length, fillStr = ' ') -> string
CommonJS entry points:
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:
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, but we haven't special namespace for that - modules es7.object.define-setter, es7.object.define-getter, es7.object.lookup-setter and es7.object.lookup-getter.
js
Object
#__defineSetter__(key, fn) -> void
#__defineGetter__(key, fn) -> void
#__lookupSetter__(key) -> fn | void
#__lookupGetter__(key) -> fn | void
CommonJS entry points:
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
core-js(/library)/stage/3
global proposal - modules es7.global and es7.system.global (obsolete)
js
global -> object
System
.global -> object (obsolete)
CommonJS entry points:
js
core-js(/library)/fn/global
core-js(/library)/fn/system/global (obsolete)
Examples:
js
global.Array === Array; // => true
Promise#finally proposal - module es7.promise.finally
js
Promise
#finally(onFinally()) -> promise
CommonJS entry points:
js
core-js(/library)/fn/promise/finally
Examples:
```js
Promise.resolve(42).finally(() => console.log('You will see it anyway'));Promise.reject(42).finally(() => console.log('You will see it anyway'));
core-js(/library)/stage/2
String#trimLeft, String#trimRight / String#trimStart, String#trimEnd proposal - modules es7.string.trim-left, es7.string.trim-right
js
String
#trimLeft() -> string
#trimRight() -> string
#trimStart() -> string
#trimEnd() -> string
CommonJS entry points:
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:
js
' hello '.trimLeft(); // => 'hello '
' hello '.trimRight(); // => ' hello'
```Symbol.asyncIterator for async iteration proposal - module es7.symbol.async-iterator
js
Symbol
.asyncIterator -> @@asyncIterator
CommonJS entry points:
js
core-js(/library)/fn/symbol/async-iterator
core-js(/library)/stage/1
Promise.try proposal - module es7.promise.try
js
Promise
.try(function()) -> promise
CommonJS entry points:
js
core-js(/library)/fn/promise/try
Examples:
``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/v2.5.5/modules/es7.array.flatten.js) and [`es7.array.flat-map`](https://github.com/zloirock/core-js/blob/v2.5.5/modules/es7.array.flat-map.js)
```js
Array
#flatten(depthArg = 1) -> array
#flatMap(fn(val, key, @), that) -> array
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
[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 - modules es7.set.of, es7.set.from, es7.map.of, es7.map.from, es7.weak-set.of, es7.weak-set.from, es7.weak-map.of, es7.weak-map.from
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:
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:
```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/v2.5.5/modules/es7.string.match-all.js)
```js
String
#matchAll(regexp) -> iterator
core-js(/library)/fn/string/match-all
core-js(/library)/fn/string/virtual/match-all
for(let [_, d, D] of '1111a2b3cccc'.matchAll(/(\d)(\D)/)){
console.log(d, D); // => 1 a, 2 b, 3 c
}
Observable proposal - modules es7.observable and es7.symbol.observable
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:
js
core-js(/library)/fn/observable
core-js(/library)/fn/symbol/observable
Examples:
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 - modules
es7.math.clamp,
es7.math.DEG_PER_RAD,
es7.math.degrees,
es7.math.fscale,
es7.math.RAD_PER_DEG,
es7.math.radians and
es7.math.scale
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:
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 - module es7.math.signbit
js
Math
.signbit(x) -> bool
CommonJS entry points:
js
core-js(/library)/fn/math/signbit
Examples:
js
Math.signbit(NaN); // => NaN
Math.signbit(1); // => true
Math.signbit(-1); // => false
Math.signbit(0); // => true
Math.signbit(-0); // => false
core-js(/library)/stage/0
String#at proposal - module es7.string.at
js
String
#at(index) -> string
CommonJS entry points:
js
core-js(/library)/fn/string/at
core-js(/library)/fn/string/virtual/at
Examples:
js
'a𠮷b'.at(1); // => '𠮷'
'a𠮷b'.at(1).length; // => 2
Map#toJSON, Set#toJSON proposal - modules es7.map.to-json, es7.set.to-json (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:
js
core-js(/library)/fn/map
core-js(/library)/fn/set
Error.isError proposal - module es7.error.is-error (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:
js
core-js(/library)/fn/error/is-error
Math.{iaddh, isubh, imulh, umulh} proposal - modules es7.math.iaddh, es7.math.isubh, es7.math.imulh and es7.math.umulh
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:
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, module es7.asap
js
asap(fn) -> void
CommonJS entry points:
js
core-js(/library)/fn/asap
Examples:
js
asap(() => console.log('called as microtask'));
core-js(/library)/stage/pre
Reflect metadata proposal - modules es7.reflect.define-metadata, es7.reflect.delete-metadata, es7.reflect.get-metadata, es7.reflect.get-metadata-keys, es7.reflect.get-own-metadata, es7.reflect.get-own-metadata-keys, es7.reflect.has-metadata, es7.reflect.has-own-metadata and es7.reflect.metadata.
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:
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:
js
var O = {};
Reflect.defineMetadata('foo', 'bar', O);
Reflect.ownKeys(O); // => []
Reflect.getOwnMetadataKeys(O); // => ['foo']
Reflect.getOwnMetadata('foo', O); // => 'bar'
core-js(/library)/web
Module web.timers. Additional arguments fix for IE9-.
setTimeout(fn(...args), time, ...args) -> id
setInterval(fn(...args), time, ...args) -> id
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);
Module web.immediate. setImmediate proposal polyfill.
setImmediate(fn(...args), ...args) -> id
clearImmediate(id) -> void
core-js(/library)/web/immediate
core-js(/library)/fn/set-immediate
core-js(/library)/fn/clear-immediate
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');
}));
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:
{
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
core-js(/library)/web/dom-collections
core-js(/library)/fn/dom-collections/iterator
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);
}
core-js(/library)/core
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
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
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
core-js(/library)/core/dict
core-js(/library)/fn/dict
Dict create object without prototype from iterable or simple object.
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.
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 equivalents of Array.prototype methods for dictionaries.
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'
Module core.function.part.
Function
#part(...args | _) -> fn(...args)
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.
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
Module core.number.iterator.
Number
#@@iterator() -> iterator
core-js(/library)/core/number
core-js(/library)/fn/number/iterator
core-js(/library)/fn/number/virtual/iterator
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]
Modules core.regexp.escape, core.string.escape-html and core.string.unescape-html.
RegExp
.escape(str) -> str
String
#escapeHTML() -> str
#unescapeHTML() -> str
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
RegExp.escape('Hello, []{}()*+?.\\^$|!'); // => 'Hello, \[\]\{\}\(\)\*\+\?\.\\\^\$\|!'
'<script>doSomething();</script>'.escapeHTML(); // => '<script>doSomething();</script>'
'<script>doSomething();</script>'.unescapeHTML(); // => '<script>doSomething();</script>'
Module core.delay. Promise-returning delay function, esdiscuss.
delay(ms) -> promise
core-js(/library)/core/delay
core-js(/library)/fn/delay
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');
})();
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
core-js(/library)/fn/is-iterable
core-js(/library)/fn/get-iterator
core-js(/library)/fn/get-iterator-method
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
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.String#normalize is not a very useful feature, but this polyfill will be very large. If you need it, you can use unorm.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.@@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.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 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.Intl is missed because of size. You can use this polyfill.