I've been looking around at JavaScript to try and get some code to load asynchronously

I found this code sample

from http://www.feedthebot.com/pagespeed/defer-loading-javascript.html

The thing is it doesn't quite do what I'm trying to achieve. I would like to be able to do something similar but setup a deferred or some type of function that is called after this has all loaded. Is that possible? If so can anyone help explain how?