Dynamically require/include a Javascript file into a page and be notified when its loaded

This is a simple little JavaScript snippet I wrote the other day that basically includes an external javascript file in an HTML page head section.

Its pretty straight forward,

it first gets a reference to the head tag.
Creates a script element using document.createElement
Sets the source/url of the file
sets the type of the script element to the correct mime type of "text/javascript"
Then sets the onload property of the script element to a callback function you supply. In i.e. it will check the onreadystatechange and execute the callback function you provide.
And finally it appends the script element to the head of the page


        /**
         *Load an externl JS file and append it to the head
         */
        function require(file,callback){
            var head=document.getElementsByTagName("head")[0];
            var script=document.createElement('script');
            script.src=file;
            script.type='text/javascript';
            //real browsers
            script.onload=callback;
            //Internet explorer
            script.onreadystatechange = function() {
                if (_this.readyState == 'complete') {
                    callback();
                }
            }
            head.appendChild(script);
        }

Probably a million and one ways to do this but it works decently in I.E 7+,Firefox,Chrome,Safari and Opera

zcourts