Package Exports

es6-shim
es6-shim/es6-sham
es6-shim/es6-shim
es6-shim/es6-shim.js

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (es6-shim) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

ES6 Shim

Provides compatibility shims so that legacy JavaScript engines behave as closely as possible to ECMAScript 6 (Harmony).

Installation

If you want to use it in browser:

Just include es6-shim before your scripts.
Include es5-shim especially if your browser doesn't support ECMAScript 5 - but every JS engine requires the es5-shim to correct broken implementations, so it's strongly recommended to always include it.

For node.js, io.js, or any npm-managed workflow (this is the recommended method):

npm install es6-shim

Alternative methods:

component install paulmillr/es6-shim if you’re using component(1).
bower install es6-shim if you’re using Bower.

In both browser and node you may also want to include unorm; see the String.prototype.normalize section for details.

Safe shims

Map, Set (requires ES5 property descriptor support)
Promise
String:
- fromCodePoint() (a standalone shim is also available)
- raw()
String.prototype:
- codePointAt() (a standalone shim is also available)
- repeat() (a standalone shim is also available)
- startsWith() (a standalone shim is also available)
- endsWith() (a standalone shim is also available)
- includes() (a standalone shim is also available)
RegExp:
- new RegExp, when given a RegExp as the pattern, will no longer throw when given a "flags" string argument. (requires ES5)
RegExp.prototype:
- flags (requires ES5) (a standalone shim is also available)
Number:
- MAX_SAFE_INTEGER
- MIN_SAFE_INTEGER
- EPSILON
- parseInt()
- parseFloat()
- isNaN()(a standalone shim is also available)
- isInteger()
- isSafeInteger()
- isFinite()
Array:
- from() (a standalone shim is also available)
- of() (a standalone shim is also available)
Array.prototype:
- copyWithin()
- fill()
- find() (a standalone shim is also available)
- findIndex() (a standalone shim is also available)
- keys() (note: keys/values/entries return an ArrayIterator object)
- entries()
- values()
Object:
- keys() (in ES5, but no longer throws on non-object non-null/undefined values in ES6)
- is() (a standalone shim is also available)
- assign() (a standalone shim is also available)
- setPrototypeOf() (IE >= 11)
Math:
- acosh()
- asinh()
- atanh()
- cbrt()
- clz32()
- cosh()
- expm1()
- hypot()
- log2()
- log10()
- log1p()
- sign()
- sinh()
- tanh()
- trunc()
- imul()
- fround()

Math functions’ accuracy is 1e-11.

Reflect
- apply()
- construct()
- defineProperty()
- deleteProperty()
- enumerate()
- get()
- getOwnPropertyDescriptor()
- getPrototypeOf()
- has()
- isExtensible()
- ownKeys()
- preventExtensions()
- set()
- setPrototypeOf()
String.prototype Annex B HTML methods These methods are part of "Annex B", which means that although they are a defacto standard, you shouldn't use them. None the less, the es6-shim provides them:
- anchor()
- big()
- blink()
- bold()
- fixed()
- fontcolor()
- fontsize()
- italics()
- link()
- small()
- strike()
- sub()
- sup()

Subclassing

The Map, Set, and Promise implementations are subclassable. You should use the following pattern to create a subclass in ES5 which will continue to work in ES6:

function MyPromise(exec) {
  Promise.call(this, exec);
  // ...
}
Object.setPrototypeOf(MyPromise, Promise);
MyPromise.prototype = Object.create(Promise.prototype, {
  constructor: { value: MyPromise }
});

String.prototype.normalize

Including a proper shim for String.prototype.normalize would increase the size of this library by a factor of more than 4. So instead we recommend that you install the unorm package alongside es6-shim if you need String.prototype.normalize. See https://github.com/paulmillr/es6-shim/issues/134 for more discussion.

WeakMap shim

It is not possible to implement WeakMap in pure javascript. The es6-collections implementation doesn't hold values strongly, which is critical for the collection. es6-shim decided to not include an incorrect shim.

WeakMap has a very unusual use-case so you probably won't need it at all (use simple Map instead).

Getting started

'abc'.startsWith('a') // true
'abc'.endsWith('a') // false
'john alice'.includes('john') // true
'123'.repeat(2)     // '123123'

Object.is(NaN, NaN) // Fixes ===. 0 isnt -0, NaN is NaN
Object.assign({a: 1}, {b: 2}) // {a: 1, b: 2}

Number.isNaN('123') // false. isNaN('123') will give true.
Number.isFinite('asd') // false. Global isFinite() will give true.
// Tests if value is a number, finite,
// >= -9007199254740992 && <= 9007199254740992 and floor(value) === value
Number.isInteger(2.4) // false.

Math.sign(400) // 1, 0 or -1 depending on sign. In this case 1.

[5, 10, 15, 10].find(function (item) {return item / 2 === 5;}) // 10
[5, 10, 15, 10].findIndex(function (item) {return item / 2 === 5;}) // 1

// Replacement for `{}` key-value storage.
// Keys can be anything.
var map = new Map();
map.set('John', 25);
map.set('Alice', 400);
map.set(['meh'], 555);
assert(map.get(['meh']) === undefined); // undefined because you need to use exactly the same object.
map.delete('Alice');
map.keys();
map.values();
assert(map.size === 2);

// Useful for storing unique items.
var set = new Set();
set.add(1);
set.add(5);
assert(set.has(1) === true);
assert(set.has(4) === false);
set.delete(5);

// Promises, see
// http://www.slideshare.net/domenicdenicola/callbacks-promises-and-coroutines-oh-my-the-evolution-of-asynchronicity-in-javascript
// https://github.com/petkaantonov/bluebird/#what-are-promises-and-why-should-i-use-them
Promise.resolve(5).then(function (value) {
  if ( ... ) throw new Error("whoops!");
  // do some stuff
  return anotherPromise();
}).catch(function (e) {
  // any errors thrown asynchronously end up here
});

Other stuff:

es6-shim