https://shunju.com/shared/js/lib/jquery.rollover.js

1$(function()
2{
3		var targetImgs = $('img');
4		
5		targetImgs.each(function()
6		{
7			if(this.src.match('_off'))
8			{
9				
10				this.rollOverImg = new Image();
11				this.rollOverImg.src = this.getAttribute("src").replace("_off", "_on");;
12				$(this.rollOverImg).css({position: 'absolute', opacity: 0});
13				$(this).before(this.rollOverImg);
14				
15				$(this.rollOverImg).mousedown(function(){
16					$(this).stop().animate({opacity: 0}, {duration: 0, queue: false});
17				});
18				
19				$(this.rollOverImg).hover(function(){
20					$(this).animate({opacity: 2}, {duration: 400, queue: false});
21				},
22				function(){
23					$(this).animate({opacity: 0}, {duration: 400, queue: false});
24				});
25				
26			}
27		});
28});