addScript.js

function addScript(src, callback) {
	var s = document.createElement('script');
	s.setAttribute('src', src);
	s.setAttribute('type', 'text/javascript');
	document.head.appendChild(s);

	if (callback !== "undefined") {
		s.onreadystatechange= function () {
			if (this.readyState == 'complete') {
				callback();
			}
		}
		s.onload= callback;
	}
}