Check if Internet Connection Exists with jQuery? [duplicate]

Answer 1

Ok, maybe a bit late in the game but what about checking with an online image? I mean, the OP needs to know if he needs to grab the Google CMD or the local JQ copy, but that doesn't mean the browser can't read Javascript no matter what, right?

<script>
function doConnectFunction() {
// Grab the GOOGLE CMD
}
function doNotConnectFunction() {
// Grab the LOCAL JQ
}

var i = new Image();
i.onload = doConnectFunction;
i.onerror = doNotConnectFunction;
// CHANGE IMAGE URL TO ANY IMAGE YOU KNOW IS LIVE
i.src = 'http://gfx2.hotmail.com/mail/uxp/w4/m4/pr014/h/s7.png?d=' + escape(Date());
// escape(Date()) is necessary to override possibility of image coming from cache
</script>

Just my 2 cents

Answer 2

The best option for your specific case might be:

Right before your close </body> tag:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/vendor/jquery-1.10.2.min.js"><\/script>')</script>

This is probably the easiest way given that your issue is centered around jQuery.

If you wanted a more robust solution you could try:

var online = navigator.onLine;

Read more about the W3C's spec on offline web apps, however be aware that this will work best in modern web browsers, doing so with older web browsers may not work as expected, or at all.

Alternatively, an XHR request to your own server isn't that bad of a method for testing your connectivity. Considering one of the other answers state that there are too many points of failure for an XHR, if your XHR is flawed when establishing it's connection then it'll also be flawed during routine use anyhow. If your site is unreachable for any reason, then your other services running on the same servers will likely be unreachable also. That decision is up to you.

I wouldn't recommend making an XHR request to someone else's service, even google.com for that matter. Make the request to your server, or not at all.

What does it mean to be "online"?

There seems to be some confusion around what being "online" means. Consider that the internet is a bunch of networks, however sometimes you're on a VPN, without access to the internet "at-large" or the world wide web. Often companies have their own networks which have limited connectivity to other external networks, therefore you could be considered "online". Being online only entails that you are connected to a network, not the availability nor reachability of the services you are trying to connect to.

To determine if a host is reachable from your network, you could do this:

function hostReachable() {

  // Handle IE and more capable browsers
  var xhr = new ( window.ActiveXObject || XMLHttpRequest )( "Microsoft.XMLHTTP" );

  // Open new request as a HEAD to the root hostname with a random param to bust the cache
  xhr.open( "HEAD", "//" + window.location.hostname + "/?rand=" + Math.floor((1 + Math.random()) * 0x10000), false );

  // Issue request and handle response
  try {
    xhr.send();
    return ( xhr.status >= 200 && (xhr.status < 300 || xhr.status === 304) );
  } catch (error) {
    return false;
  }

}

You can also find the Gist for that here: https://gist.github.com/jpsilvashy/5725579

Details on local implementation

Some people have commented, "I'm always being returned false". That's because you're probably testing it out on your local server. Whatever server you're making the request to, you'll need to be able to respond to the HEAD request, that of course can be changed to a GET if you want.

Answer 3

A much simpler solution:

<script language="javascript" src="http://maps.google.com/maps/api/js?v=3.2&sensor=false"></script>

and later in the code:

var online;
// check whether this function works (online only)
try {
  var x = google.maps.MapTypeId.TERRAIN;
  online = true;
} catch (e) {
  online = false;
}
console.log(online);

When not online the google script will not be loaded thus resulting in an error where an exception will be thrown.

Answer 4

I wrote a jQuery plugin for doing this. By default it checks the current URL (because that's already loaded once from the Web) or you can specify a URL to use as an argument. Always doing a request to Google isn't the best idea because it's blocked in different countries at different times. Also you might be at the mercy of what the connection across a particular ocean/weather front/political climate might be like that day.

http://tomriley.net/blog/archives/111

Answer 5

You can try by sending XHR Requests a few times, and then if you get errors it means there's a problem with the internet connection.

Edit: I found this JQuery script which is doing what you are asking for, I didn't test it though.

Answer 6

You can mimic the Ping command.

Use Ajax to request a timestamp to your own server, define a timer using setTimeout to 5 seconds, if theres no response it try again.

If there's no response in 4 attempts, you can suppose that internet is down.

So you can check using this routine in regular intervals like 1 or 3 minutes.

That seems a good and clean solution for me.