In an effort to better my javascript skills… I needed a way to hook
into the window.onload event.  Rather than just doing something
like window.onload = Load_EventHandler();
I decided that I would add an event listener to the load event,
instead… But how to do that so that it is cross-browser supported (IE
6+ and Gecko is all I really care about, personally)?  This is
what I came up with (with example usage):

function AttachEvent(elementObj, eventName, eventHandlerFunctionName)
{
  if (elementObj.addEventListener) 
  { // Non-IE browsers
    elementObj.addEventListener(eventName, eventHandlerFunctionName, false);		
  } 
  else if (elementObj.attachEvent) 
  { // IE 6+
    elementObj.attachEvent('on' + eventName, eventHandlerFunctionName);
  } 
  else 
  { // Older browsers 
    var currentEventHandler = elementObj['on' + eventName];
    if (currentEventHandler == null) 
    {
      elementObj['on' + eventName] = eventHandlerFunctionName;
    } 
    else 
    {
      elementObj['on' + eventName] = function(e) { currentEventHandler(e); eventHandlerFunctionName(e); }
    }
  }
}

// @eventArgs is an interface of type Event: http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-Event
function Load_EventHandler(eventArgs)
{
  alert("here");
}

AttachEvent(window, "load", Load_EventHandler);