polyfill.io.md

   1 ---
   2 title: Polyfill.io
   3 category: JavaScript libraries
   4 updated: 2018-08-20
   5 layout: 2017/sheet
   6 intro: |
   7   [Polyfill.io](https://polyfill.io) is a service that serves JavaScript polyfills.
   8 ---
   9
  10 ## Usage
  11
  12 ### Default usage
  13
  14 ```html
  15 <script src="https://cdn.polyfill.io/v2/polyfill.min.js"></script>
  16 ```
  17 {: .-wrap}
  18
  19 This is the default script for Polyfill.io.
  20
  21 ### References
  22
  23 * [API example](https://polyfill.io/v2/docs/api) _(polyfill.io)_
  24 * [List of features](https://polyfill.io/v2/docs/features) _(polyfill.io)_
  25
  26 ## Optimized
  27
  28 ### For modern browsers
  29
  30 ```html
  31 <script>if(!(window.Promise&&[].includes&&Object.assign&&window.Map)){document.write('<script src="https://cdn.polyfill.io/v2/polyfill.min.js"></scr'+'ipt>')}</script>
  32 ```
  33
  34 This only includes polyfill.io when necessary, skipping it for modern browsers for faster load times.
  35
  36 ### Extra features
  37
  38 ```html
  39 <script>if(!(window.fetch&&window.Promise&&[].includes&&Object.assign&&window.Map)){document.write('<script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=default,fetch"></scr'+'ipt>')}</script>
  40 ```
  41
  42 This is the same as the previous, but also adds a polyfill for `window.fetch()`. We add a `window.fetch` check and loads the additional `fetch` feature.