[getScript]

gistfile1.js

function getScript(url, success) {
  var script = document.createElement('script');
	script.src = url;
	var head = document.getElementsByTagName('head')[0],
		done = false;
	// Attach handlers for all browsers
	script.onload = script.onreadystatechange = function() {
		if(!done && (!this.readyState || this.readyState == 'loaded' || this.readyState == 'complete')) {
			done = true;
			success();
			script.onload = script.onreadystatechange = null;
			head.removeChild(script);
		}
	};
	head.appendChild(script);
}

//example
getScript('http://code.jquery.com/jquery.min.js', function() {
	if(typeof jQuery == 'undefined') {
		alert('Load Failed');
	} else {
		alert('Load Success. (jQuery v' + jQuery.fn.jquery + ')');
	}
});