Created: 2011-07-09 00:55
Updated: 2018-12-05 15:23
License: isc



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Version: 2.0.0

Copyright 2015 James Brumond

Licensed under ISC

A JavaScript Polyfill Framework

polyfill.js is a very lightweight JavaScript framework for replacing missing features in outdated browsers. It can be loaded simply by adding the following script tag to your document:

<script type="text/javascript" src="http://polyfill.herokuapp.com/core"></script>

The core for polyfill.js is extremely small and you only have to load the polyfills you need. For example, if you want to use localStorage, EventSource, and Array.prototype.forEach in your application, you tell polyfill.js that you need them, it checks if you already have them, and then loads only what you need. You would do this by using the Polyfill.needs() method, like this:

Polyfill.needs(['localstorage', 'eventsource', 'foreach'], function() {
    // Do something with those functionalities

Now, let's assume that your browser has localStorage, but not EventSource or forEach. polyfill.js figures this out and dynamically includes a script that loads polyfills for just those features. That request would look like this:


That loaded script is a compacted (using uglify-js) and gzipped package containing your polyfills. Nothing extra. No waste.

Available Polyfills

  • hashchange (window.onhashchange)
  • json (window.JSON/*.prototype.toJSON)
  • storage (window.localStorage)
  • placeholder (HTML5 input placeholder attribute)
  • queryselectorall (document.querySelector[All])
  • xhr (window.XMLHttpRequest)
  • eventsource (window.EventSource)
  • promise (window.Promise)
  • trim (String.prototype.trim)
  • filter (Array.prototype.filter)
  • foreach (Array.prototype.foreach)
  • indexof (Array.prototype.indexOf)
  • map (Array.prototype.map)
  • every (Array.prototype.every)
  • some (Array.prototype.some)
  • reduce (Array.prototype.reduce)
  • reduceright (Array.prototype.reduceRight)
  • lastindexof (Array.prototype.lastIndexOf)
  • bind (Function.prototype.bind)
  • toisostring (Date.prototype.toISOString)
  • setimmediate (window.setImmediate)
  • keys (Object.keys)
  • isarray (Array.isArray)
  • now (Date.now)
  • dateparse (Date.parse)
  • requestanimationframe (window.requestAnimationFrame)
  • classlist (element.classList)

Contributing A New Polyfill

I am still looking for more polyfills to add to this collection. If you have built a polyfill and would like it added, feel free to open an issue with more information, or send a pull request (but please stick to the conventions already in use in the code). Also, any polyfills should run completely automatically (they should require no extra action by developers to use) and should follow the appropriate specification as closely as possible.

Running the server

To run your own instance of the polyfill server, the first thing you need to do is to pull down the code.

$ git clone git://github.com/kbjr/polyfill.js.git
$ cd polyfill.js

You will need node.js @0.12.x, so make sure you have that. Then, install the dependencies:

$ npm install

Next, open up the config.js file. There are a few things here you can play with, but nothing all that impressive. We're looking for the baseUrl value. You need to change that to the origin you will be running the server on. (note: this value needs to have a trailing slash, it won't work without one). At this point, the server can be started.

$ node server/app.js

Special Thanks To

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