How to tell if a <script> tag failed to load

javascript onerror script-tag
David picture David · Feb 11, 2009 · Viewed 127.3k times · Source

I'm dynamically adding <script> tags to a page's <head>, and I'd like to be able to tell whether the loading failed in some way -- a 404, a script error in the loaded script, whatever.

In Firefox, this works:

var script_tag = document.createElement('script');
script_tag.setAttribute('type', 'text/javascript');
script_tag.setAttribute('src', 'http://fail.org/nonexistant.js');
script_tag.onerror = function() { alert("Loading failed!"); }
document.getElementsByTagName('head')[0].appendChild(script_tag);

However, this doesn't work in IE or Safari.

Does anyone know of a way to make this work in browsers other than Firefox?

(I don't think a solution that requires placing special code within the .js files is a good one. It's inelegant and inflexible.)

Answer

Diodeus - James MacFarlane picture Diodeus - James MacFarlane · Feb 11, 2009

There is no error event for the script tag. You can tell when it is successful, and assume that it has not loaded after a timeout:

<script type="text/javascript" onload="loaded=1" src="....js"></script>

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