Skip to content
This repository

ECMAScript 6 (Harmony) compatibility shims for legacy JavaScript engines

Fetching latest commit…

Cannot retrieve the latest commit at this time

README.md

ES6 Shim

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

Project targets engines that support ES5 (Firefox, Chrome, Safari, Opera). With ES5-shim it could also work in older browsers.

Installation

npm install es6-shim

Or just include es6-shim before your scripts if you want to use it in browser.

Safe shims

  • Maps & Sets
  • String.prototype.repeat, String.prototype.startsWith, String.prototype.endsWith, String.prototype.contains
  • Array.from, Array.of
  • Number.MAX_INTEGER, Number.EPSILON, Number.parseInt, Number.parseFloat, Number.isNaN, Number.toInteger, Number.isInteger, Number.isFinite
  • Object.getOwnPropertyDescriptors, Object.getPropertyDescriptor, Object.getPropertyNames, Object.is, Object.isnt
  • Math.sign, Math.log10, Math.log2, Math.log1p, Math.expm1, Math.cosh, Math.sinh, Math.tanh, Math.acosh, Math.asinh, Math.atanh, Math.hypot, Math.trunc (accuracy is 1e-11).

WeakMap shim

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

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

IE8 support

There are some shims that do not work in IE8, because it is simply not possible to implement them properly:

  • Object.getOwnPropertyDescriptors, Object.getPropertyDescriptor, Object.getPropertyNames

Getting started

'abc'.startsWith('a') // true
'abc'.endsWith('a') // false
Object.is(NaN, NaN) // Fixes ===. 0 isnt -0, NaN is NaN
'123'.repeat(2)     // '123123'
'john alice'.contains('john') // true
Number.isNaN('123') // false. isNaN('123') 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.
Number.isFinite('asd') // false. Global isFinite() will give true.
Math.sign(400) // 1, 0 or -1 depending on sign. In this case 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')

// 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)

Copyright (c) 2012 Paul Miller (http://paulmillr.com)

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.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Something went wrong with that request. Please try again.