# Polyfills

## Babel

當使用語言的新特性，瀏覽器不一樣支援，這時候要使用轉譯器將程式碼轉為較老舊瀏覽器支援的寫法。Babel 包含2 個部分；

1. 轉譯程式，將重新改寫程式碼轉為老舊支援的寫法，webpack 就提供了這樣自動轉譯的功能，對於工程師來說沒有時間的損失。
2. polyfill 新的特性包含內建函式跟語法結構，轉譯器可以轉譯成就的語法結構，但新的函式需要額外加上去。

*  [babel polyfill](https://babeljs.io/docs/usage/polyfill/) 支援很多函式，但吃資源
*  [polyfill.io](http://polyfill.io/) 可以視需求加需要的功能

 [Chrome Canary](https://www.google.com/chrome/browser/canary.html) 可以使用所有新特性。


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