ECMAScript 6 (Harmony) compatibility shims for legacy JavaScript engines
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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

Safe shims

  • Maps & Sets
  • String.prototype.repeat, String.prototype.startsWith, String.prototype.endsWith, String.prototype.contains, String.prototype.toArray
  • Array.from, Array.of
  • 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

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).

es6-collections Map and Set are also implemented incorrectly and don't pass all V8 collection tests.

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

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.