browser-support

This library allows websites to maintain compatibility with older browsers, which do not implement newer features. It does so using polyfills for small new features, plus functions to determine if a browser supports a set of features natively or with polyfills.

If you would like to see what features the browser you are currently using implements, you can visit the documentation site which displays a compatibility table that detects which features are natively supported in your browser.

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We use all of these polyfills on GitHub.com. We also use the isSupported() function to determine if the browser meets a minimum set of functionality which we expect, browser that return false from isSupported() do not send errors or statistics to our backend monitoring.

Installation

``
$ npm install @github/browser-support
`

Usage

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`js
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)
}
`

Development

`
npm install
npm test
`

Upgrading browser-support in Dotcom

During upgrades, it is crucial to ensure that browser error reporting to Sentry is not disrupted. Use the following steps to validate this functionality:

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- Create a PR to upgrade the browser-support version in Dotcom.
- Trigger a browser error from your review-lab instance and confirm it is reported in Sentry:
- Append #b00m to your review-lab URL (e.g. https://branchname.review-lab.github.com#b00m) and refresh the page.
- Confirm the error is reported in review-lab Sentry.
- Perform these steps in Chrome, Firefox, Edge, and Opera. Note: Errors are currently not reported in Safari due to an open issue.

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- Check the browser-reporting monitor.
- If the rate of reported browser errors drops, the monitor will trigger an alert in the #web-systems-ops channel.
- After deploying to canary:
- Trigger a browser error by appending #b00m to your URL.
- Confirm the error is reported in canary Sentry.
- After deploying to production:
- Trigger a browser error by appending #b00m to your URL.
- Confirm the error is reported in production Sentry.
- Check the browser-reporting monitor to ensure there are no anomalies in the error reporting rate.

Contributing

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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.

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Polyfills should only be removed after consulting with the @github/web-systems who will determine if a polyfill can be removed. 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.

License

Distributed under the MIT license. See LICENSE for details.