https://github.com/cvan/navigator.online-that-actually-works

it really does
https://github.com/cvan/navigator.online-that-actually-works

Last synced: 4 months ago
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it really does

• Host: GitHub
• URL: https://github.com/cvan/navigator.online-that-actually-works
• Owner: cvan
• License: mit
• Created: 2014-09-17T21:35:03.000Z (over 10 years ago)
• Default Branch: gh-pages
• Last Pushed: 2014-09-18T03:28:04.000Z (over 10 years ago)
• Last Synced: 2024-04-10T09:23:19.720Z (10 months ago)
• Language: JavaScript
• Size: 141 KB
• Stars: 6
• Watchers: 2
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# navigator.onLine-that-actually works

Fixing `navigator.onLine` so it works everywhere.

## What is `navigator.onLine`, mate?

> `window.navigator.onLine`

>

> Returns `false` if the user agent is definitely offline (disconnected from the network). Returns `true` if the user agent might be online.

>

> The events online and offline are fired when the value of this attribute changes.

>

> Note: This attribute is inherently unreliable. A computer can be connected to a network without having Internet access.

Source: [HTML Standard](https://html.spec.whatwg.org/#browser-state)

## What's the problem, mate?

`navigator.onLine` [always incorrectly reports `true` in Firefox](https://bugzilla.mozilla.org/show_bug.cgi?id=654579) and doesn't fire events [bug 756364](https://bugzilla.mozilla.org/show_bug.cgi?id=756364). And there are a [plethora of bugs with Chrome's implementation](http://crbug.com?q=navigator.online) too.

## What can we do about it, mate?

We have a few options:

* check for connectivity only when a user action that requires connectivity, polling only until user regains connectivity

* continually make a simple request in the background, fixing the value of `navigator.onLine` and firing events ([@remy](https://github.com/remy)'s example uses synchronous XHR polling every 5 minutes)

* change `navigator.onLine` to return a `Promise` that eventually resolves when user regains connectivity

* XHR long-polling beacon

* checking when a [socket](https://developer.mozilla.org/en-US/docs/Web/API/TCPSocket) is closed, which unfortunately works on only Firefox OS for privileged, packaged web apps ([raw sockets are currently being standardised](http://www.w3.org/TR/raw-sockets/))

* checking when a WebSocket is closed

## Credits

A big thanks to [@remy](https://github.com/remy) for his [XHR-polling polyfill](https://github.com/remy/polyfills/blob/master/offline-events.js).

I want to thank these fine individuals for their assistance in extending [my original concept](ondemand-promises.js) and building out a full-blown, resilient offline-checking system in the [Firefox Marketplace](https://github.com/mozilla/fireplace):

* [@muffinresearch](https://github.com/remy)

* [@spasovski](https://github.com/spasovski)

* [@diox](https://github.com/diox)

* [@ngokevin](https://github.com/ngokevin)

## Licence

The content of this project itself is licenced under the [Creative Commons Attribution 3.0 licence](http://creativecommons.org/licences/by/3.0/us/deed), and the underlying source code used to format and display that content is licenced under the [MIT licence](LICENCE).