Example of how to dynamically load and run JS

dynamic.loader.js

// Function for adding JS to window load event
function myAddLoadEvent(f) {
	var oldonload = window.onload;
	if (typeof window.onload != 'function') {
		window.onload = f;
	} else {
		window.onload = function() {
			if (oldonload) {
				oldonload();
			}
			f();
		}
	}
}

// On page load add custom JS and run myCustomInit
myAddLoadEvent(function() {
	var head = document.getElementsByTagName("head")[0];         
	var newScript = document.createElement('script');
	newScript.type = 'text/javascript';
	newScript.src = 'http://domain.com/mycustom.js';
	newScript.onload = myCustomInit;
	head.appendChild(newScript);
});

// Perform functions dependent on mycustom.js
function myCustomInit() {
	// foo bar
}