[bullant]

Originally Posted by Old Pedant

I wonder if you couldn't use an AJAX call to try to download the contents of the script? .

Not if it's on a different domain.

If it's on the same domain you could send a head request to see if the url exists.

A simplified example

 
           var url='http://www.yourdomain.com';
            xmlHttp = new XMLHttpRequest();
            xmlHttp.open('HEAD', url, false);
            xmlHttp.send();
            alert(xmlHttp.status);