jQuery CDN timeout fallback

Question

I have read in several places how to fallback on a local copy of the jQuery library should the link hosted by either google or microsoft or other fail.

<script type="text/javascript" src="http://ajax.microsoft.com/ajax/jquery/jquery-1.3.2.min.js"></script>
<script type="text/javascript">
if (typeof jQuery == 'undefined')
{
document.write(unescape("%3Cscript src='/Scripts/jquery-1.3.2.min.js' type='text/javascript'%3E%3C/script%3E"));
}
</script>

My application works within an intranet environment however and occasionally the external jQuery link doesn't so much fail but takes a long time to load (due to external internet connection issues).

I'm wondering if there is a way to not only use such a fallback but set a timeout for the CDN link so that if the link takes a certain amount of time it should fail and call on the fallback.

Something like:

if(timetoloadjquery > n) {
    Use fallback local jQuery library.
}

Perhaps some kind of loop that checks if the jQuery is defined and if after so many iterations it is not....do something else?

Thanks for the help.

Answer 1

This may help you. After 5-seconds have passed, Javascript checks if jQuery is available, if not, then loads the library from local server.

1. With a timer

<script>
setTimeout(function() {
  if(window.jQuery) return;
  var n = document.getElementsByTagName("script")[0];
  n.parentNode.insertBefore(document.createElement("script"), n).src = "assets/jQuery/jquery-1.7.2.min.js";
}, 5000);
</script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.7.0/jquery.min.js"></script>

2. This one doesn't have a timer, it loads a local version if the CDN version fails.

<script type="text/javascript" src="//ajax.googleapis.com/ajax/libs/jquery/1.8.3/jquery.js"></script>
<script type="text/javascript">window.jQuery || document.write("<script type='text/javascript' src='js/jquery-1.8.3.min.js'>\x3C/script>")</script>