polyfill - JavaScript Polyfills, Shims and More

• A shim lets you write the same code across all browsers by implementing a new API in downlevel browsers.
• A polyfill is a shim or collection of shims (and a catchy name).
• A prollyfill is a shim for a proposed API
• A helper helps write cross-browser code where a true API shim/polyfill is not possible.

My philosophy is that it's better to write future-looking code that takes advantage of new Web platform APIs where possible, and fill in the gaps with polyfills. There is no effort to produce 100% compliant behavior, or to completely hide differences in browser behavior.

I use these in various pages on my sites; most are by me, or I have at least tweaked them. A more comprehensive list of polyfills can be found at The All-In-One Entirely-Not-Alphabetical No-Bullshit Guide to HTML5 Fallbacks by Paul Irish.

Getting the Code

You're already here! Great, just download it, or use:

git: git clone https://github.com/inexorabletash/polyfill.git

bower: bower install js-polyfills

npm: npm install js-polyfills

It is not packaged as Node.js module(s); there's nothing to require(), this is just for distribution.

Or just include scripts directly in your page via CDN (c/o RawGit):

<script src="https://cdn.rawgit.com/inexorabletash/polyfill/$TAGNAME/polyfill.min.js"></script>

(look at Releases for the tag name, e.g. "v1.2.3")

Files

The polyfills are roughly split up into files matching 1:1 with Web standards (specifications, living standards documents, etc). So there is html.js for HTML, dom.js for DOM, etc.

Since I generally use several in my hobby projects, bundled/minified versions are available:

• web.js (minified: web.min.js) includes the most common Web polyfills - it assumes ES2015 support
  • Includes: html.js dom.js xhr.js cssom.js url.js fetch.js
• polyfill.js (minified: polyfill.min.js) has everything in web.js plus es5.js and es6.js and es2016.js

Minification is done via https://github.com/mishoo/UglifyJS2

ECMAScript / JavaScript Polyfills

ECMAScript 5 - Previous standard, supported by browsers circa 2012..

ECMAScript 2015 - Previous standard, supported by browsers circa 2016.

ECMAScript 2016 - Most recent standard. Not fully supported by modern browsers yet.

ECMAScript proposed - Proposals for future editions of the standard. Here there be dragons.

JavaScript 1.X String Extras - ref

• String prototype: trimLeft, trimRight, quote

HTML

script - tests - living standard

• document.head (for IE8-)
• 'shiv' of newer HTML elements (section, aside, etc), to fix parsing (for IE8-)
• dataset and data-* attributes spec (for IE8+, not available in IE7-)
  • str = element.dataset[key] - yields undefined if data-key attribute not present
  • element.dataset[key] = str - fails unless data-key attribute already present
• Base64 utility methods (for IE9-)
  • encodedString = window.btoa(binaryString) - Base64 Encode
  • binaryString = window.atob(encodedString) - Base64 Decode
• Animation Frames - demo page
  • id = window.requestAnimationFrame()
  • window.cancelAnimationFrame(id)

DOM

script - tests - living standard

• Selectors (for IE7-) - adapted from Paul Young
  • element = document.querySelector(selector)
  • elementArray = document.querySelectorAll(selector)
• elem.matches(selector) (for IE, Firefox 3.6, early Webkit and Opera 15.0)
• elementArray = document.getElementsByClassName(classNames) (for IE8-)
• e = element.nextElementSibling, e = element.previousElementSibling (for IE8)
• Node constants: Node.ELEMENT_NODE, etc (for IE8-)
• DOMException constants: DOMException.INDEX_SIZE_ERR (for IE8-)
• Events (for IE8)
  • Where EventTarget is window, document, or any element:
    • EventTarget.addEventListener(event, handler) - for IE8+
    • EventTarget.removeEventListener(event, handler) - for IE8+
  • Event: target, currentTarget, eventPhase, bubbles, cancelable, timeStamp, defaultPrevented, stopPropagation(), cancelBubble()
• Non-standard Event helpers for IE7- - adapted from QuirksMode
  • window.addEvent(EventTarget, event, handler)
  • window.removeEvent(EventTarget, event, handler)
• DOMTokenList - classListspec, relListspec
  • DOMTokenList: length, item(index), contains(token), add(token), remove(token), toggle(token)
  • tokenList = elem.classList - for IE8+
  • tokenList = elem.relList - for IE8+
  • Non-standard helpers for IE7-:
    • tokenList = window.getClassList(element)
    • tokenList = window.getRelList(element)
• ParentNode: node.prepend(nodes...), node.append(nodes...)
• ChildNode: node.before(nodes...) , node.after(nodes...) , node.replaceWith(nodes...) , node.remove()

Fetch

script - tests - living standard

Example:

fetch('http://example.com/foo.json')
  .then(function(response) { return response.json(); })
  .then(function(data) { console.log(data); });

Supported:

• Headers: new Headers(), append(name, value), delete(name), get(name), getAll(name), has(name), set(name, value), [Symbol.iterator]()
• Body: arrayBuffer(), blob(), formData(), json(), text() - but conversions are limited
• Request: new Request(input, init), method, headers, body, url
• Response: new Response(body, init), headers, url, status, statusText, body
• fetch(input, init)

XMLHttpRequest

script - tests - living standard

• XMLHttpRequest (for IE6-)
• FormData (for IE9-)

CSS OM

script - spec

Polyfill for width and height in getBoundingClientRect() in IE8-

URL API

script - tests - living standard

var url = new URL(url, base);
var value = url.searchParams.get(name);
var valueArray = url.searchParams.getAll(name);
url.searchParams.append(name, valueOrValues);
url.searchParams.delete(name);

var p = new URLSearchParams('a=1&b=2');

• URL: href, origin, protocol, username, password, host, hostname, port, pathname, search, searchParams, hash
• URLSearchParams: append(name, value), delete(name), get(name), getAll(name), has(name), set(name, value), entries(), keys(), values(), forEach(callback) and [Symbol.iterator]() (if defined)

Uncommon Polyfills

The following are of limited use and are not included in the web.js / polyfill.js bundled versions.

Timing

script

• Efficient Script Yielding
  • id = setImmediate(callback, args...)
  • clearImmediate(id)

Keyboard Events

script - demo page - draft spec (also)

KeyboardEvent: code, key, location, KeyboardEvent.queryKeyCap(code)

IE7- only: Call window.identifyKey(keyboardEvent); in keydown/keyup handlers before accessing above properties.

more details

Geolocation API

script - demo page - spec - uses freegeoip.net

navigator.geolocation.getCurrentPosition(successCallback, errorCallback, options);
var watchId = navigator.geolocation.watchPosition(successCallback, errorCallback, options);
navigator.geolocation.clearWatch(watchId);

Obsolete

Obsolete and Unmaintained Polyfills