core-js-ie8
v2.0.3
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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.
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
- Supported engines
- Features
- 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 upcore-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:
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
core-js(/library)/es5
ECMAScript 6
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
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
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
core-js/es6/function
core-js/fn/function/name
core-js/fn/function/has-instance
(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)
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
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)
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
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"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
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
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
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
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
core-js/es6/date
core-js/fn/date/to-string
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
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
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
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
andSymbol.keyFor
can't be shimmed cross-realm.- By default, to hide the keys,
Symbol
polyfill defines setter inObject.prototype
. For this reason, uncontrolled creation of symbols can cause memory leak and thein
operator is not working correctly withSymbol
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 toObject.prototype
for well-known symbols for correct work something likeSymbol.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)
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
}
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)
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
}
WeakMap
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'
WeakSet
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
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
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
}
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+)
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
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
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 - modulees7.array.includes
,%TypedArray%
version in modules from this section.
core-js(/library)/stage/4
core-js(/library)/fn/array/includes
Stage 3:
Object.values
,Object.entries
proposal - moduleses7.object.values
,es7.object.entries
String#padStart
,String#padEnd
proposal - moduleses7.string.pad-left
,es7.string.pad-right
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.
core-js(/library)/stage/2
Stage 1:
String#trimLeft
,String#trimRight
/String#trimStart
,String#trimEnd
proposal - moduleses7.string.trim-left
,es7.string.trim-right
System.global
proposal - modulees7.system.global
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 - modulees7.string.at
Object.getOwnPropertyDescriptors
proposal - modulees7.object.get-own-property-descriptors
Map#toJSON
,Set#toJSON
proposal - moduleses7.map.to-json
,es7.set.to-json
Error.isError
proposal - modulees7.error.is-error
Math.{iaddh, isubh, imulh, umulh}
proposal - moduleses7.math.iaddh
,es7.math.isubh
,es7.math.imulh
andes7.math.umulh
.
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.
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
[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
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
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
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');
}));
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)
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);
}
Non-standard
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
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.prot