CODEWITHSUNDEEP
javascriptajax
LibertasMens
LibertasMens

Reputation: 31

Checking if the Internet and a particular site are up in JavaScript/AJAX

I have a page which runs locally on my device, and I would like to use AJAX or normal JavaScript to check if the device is connected to the Internet and if a particular site is up.

Additionally, I'm trying to figure out how to count the number of entries in an RSS feed through AJAX, but I've never programmed around RSS before. This isn't as big of a priority, though.

Upvotes: 1

Views: 301

Answers (3)

Robin Drexler
Robin Drexler

Reputation: 4457

There is basic support for

navigator.online
//Events
window.onOnline
window.onOffline

on desktop browsers and support on Android. This might not completely answer your question, but I thought its worth sharing anyway :)

Upvotes: 0

apsillers
apsillers

Reputation: 116030

Unlike Ajax, the loading of scripts and images is not subject to the same-origin policy, so you can query for their existence (but not read their contents) cross-domain. If you know a particular image on the site, you can use the onload event handler of a new Image to test if a site is up:

var i = new Image();
i.onload = function() { alert("site is up!") }
i.onerror = function() { alert("site is not up!") }
i.src = "/favicon.ico";

/favicon.ico is on a huge number of major sites, since it's required for favicon functionality in older IE. Not every site of the Web has it (indeed, not every site on the Web has a favicon), but it will work for major sites like Google, Wikipedia, Stack Overflow, etc.

/favicon.ico is nice for cross-site support, but if you only want to target one specific site, simply find an image on that site and query for its existence.

Upvotes: 3

SReject
SReject

Reputation: 3936

Cross site Ajax is forbidden due to security concerns. A few work arounds would be to either use greasemonkey/userscripts(if this is just for personal use), or a plugin such as flash or java

Upvotes: 1

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