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 if your browser doesn't support ECMAScript 5.
component install paulmillr/es6-shim if you’re using component(1).
bower install es6-shim if you’re using Twitter Bower.

For node.js:

npm install es6-shim

Safe shims

Map, Set (requires ES5)
String:
- fromCodePoint()
- raw()
String.prototype:
- codePointAt()
- repeat()
- startsWith()
- endsWith()
- contains()
Number:
- MAX_SAFE_INTEGER
- EPSILON
- parseInt()
- parseFloat()
- isNaN()
- isSafeInteger()
- isFinite()
Number.prototype:
- clz()
Array:
- from()
- of()
Array.prototype:
- find()
- findIndex()
- keys() (note: keys/values/entries return an ArrayIterator object)
- entries()
- values()
Object:
- getOwnPropertyDescriptors() (ES5)
- getPropertyDescriptor() (ES5)
- getPropertyNames() (ES5)
- is()
- assign()
- mixin() (ES5)
Math:
- sign()
- log10()
- log2()
- log1p()
- expm1()
- cosh()
- sinh()
- tanh()
- acosh()
- asinh()
- atanh()
- hypot()
- trunc()
- imul()

Math functions accuracy is 1e-11.

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'.contains('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}
Object.mixin({a: 1}, {get b: function() {return 2}}) // {a: 1, b: getter}

Number.isNaN('123') // false. isNaN('123') will give true.
Number.isFinite('asd') // false. Global isFinite() will give true.
Number.toInteger(2.4) // 2. converts values to IEEE754 double precision integers
// 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)
map.get(['meh']) // undefined because you need to use exactly the same object.
map.delete('Alice')
map.keys()
map.values()
map.size // 2

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

Other stuff:

License

The project was initially based on es6-shim by Axel Rauschmayer.

The MIT License (MIT)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.