Add an Event Cross-Browser

This is a method that checks for the standard addEventListener() or ActiveX's attachEvent() and will assign the event appropriately depending on the browser accessing the page.

                                function addEvent(elem, event, func){  
		elem.addEventListener(event, func, false);  
	}else if(document.attachEvent){  
		elem.attachEvent('on' + event, func);  
		elem['on' + event] = func;  

Here is how it can be used.

                                // passing anonymous function
addEvent(window, 'load', function(){  
	// any code to run
addEvent(someForm, 'keyup', validateField);