(JavaScript) How to load local script files as fallback in cases where CDN are blocked/unavailable?

http://stackoverflow.com/questions/5257923/how-to-load-local-script-files-as-fallback-in-cases-where-cdn-are-blocked-unavai

 

 

To confirm that cdn script loaded you can check for existence any variable/function this script defines, if it is undefined - then cdn failed and you need to load local script copy.

On this principle are based solutions like that:

<script src="//ajax.googleapis.com/ajax/libs/jquery/1.5.1/jquery.min.js"></script>
<script>window.jQuery || document.write('<script src="js/libs/jquery-1.5.1.min.js">\x3C/script>')</script>

(if there is no window.jQuery property defined cdn script didn't loaded).

 

 

<\/script> works fine, too.

 

if (typeof(window.jQuery) === 'undefined') document.write('<script src="js/libs/jquery-1.5.1.min.js"><\/script>')