Dynamically load a javascript file

loadscript.js

function loadScript(src, callback) {
    var head = document.getElementsByTagName('head')[0];
    var new_script = document.createElement('script');
    new_script.type = 'text/javascript';
    new_script.src = src;

    // most browsers
    new_script.onload = callback;

    // IE 6 & 7
    new_script.onreadystatechange = function() {
	if (this.readyState == 'complete') {
	    callback();
	}
    };

    head.appendChild(new_script);
}