//These functions allow you to set a handler for a mouseleave/enter event
//Note that the mouseout/over handler is always executed before the mouseleave/enter handler
//Also note that mouseleave/enter events do not bubble; effectively, they don't bubble in this implementation either.
//usage:  elem.onmouseout = onMouseOutLeave(outHandler_or_null, leaveHandler);
//usage:  elem.onmouseover = onMouseOverEnter(overHandler_or_null, enterHandler);
function onMouseOutLeave(handleOut, handleLeave)
{
	return function(evt)
	{
		evt = evt || window.event;
		
		var ret = true;
		if(handleOut) ret = handleOut.call(this, evt);
		
		if(evt.type != "mouseout" || !handleLeave) return ret;
		
		var from = this;
		var to = evt.relatedTarget || evt.toElement;
		
		var tmp = to;
		do
		{
			if(tmp == from) return ret;	//didn't leave; entered a child element
			tmp = tmp.parentNode;
		}while(tmp)
		
		return ret && handleLeave.call(this, evt);
	}
}
function onMouseOverEnter(handleOver, handleEnter)
{
	return function(evt)
	{
		evt = evt || window.event;
		
		var ret = true;
		if(handleOver) ret = handleOver.call(this, evt);
		
		if(evt.type != "mouseover" || !handleEnter) return ret;
		
		var to = this;
		var from = evt.relatedTarget || evt.fromElement || this;
		//when the page loads, if the mouse is already inside the element and is then moved, the mouseover event fires. There is no source
		// element in that case so I set `from` to itself
		
		var tmp = from;
		do
		{
			if(tmp == to) return ret;	//didn't enter; left a child element
			tmp = tmp.parentNode;
		}while(tmp)
		
		return ret && handleEnter.call(this, evt);
	}
}

These functions allow you to set a handler for a mouseleave/enter event.

MouseEnter/Leave Handlers 2

javascript, event

JavaScript