Polyfills for small new features, plus functions to determine browser feature support.

We use all of these polyfills on GitHub.com. We also use the isSupported() function to determine if the browser is well supported, unsupported browsers do not send errors or statistics to our backend monitoring.

$ npm install @github/browser-support

import {isSupported, isPolyfilled, apply} from '@github/browser-support'

// Check if a browser is supported
if (!isSupported()) {
  apply()
  console.assert(isSupported() === true)
  console.assert(isPolyfilled() === true)
}

npm install
npm test

Please do not add any polyfills for ECMA features that are Stage 3 or below. We only wish to polyfill features from ECMAScript that are Stage 4 (about to be included in a new years specification) or already specified.

When our supported browsers (see github/github for details) all support a feature without polyfills, we can remove the polyfill. This code is designed to be kept lightweight, we do not want to ship dozens of kb of polyfills.

As a polyfill is removed, it may be worth adding feature detection to the baseSupport const, to ensure that our baseline moves with our browser support matrix.

Distributed under the MIT license. See LICENSE for details.