https://www.fukuoka-cambodia.jp/common/js/rollover.js

1new function(){
2	function rollover(){
3		var targetClassName = "rollover";
4		var suffix = "_on";
5
6		var overReg = new RegExp("^(.+)(\\.[a-z]+)$");
7		var outReg = new RegExp("^(.+)" + suffix + "(\\.[a-z]+)$");
8
9		var preload = new Array();
10		var images = document.getElementsByTagName("img");
11
12		for (var i = 0, il = images.length; i < il; i++) {
13			var classStr = images[i].getAttribute("class") || images[i].className;
14			var classNames = classStr.split(/\s+/);
15			for(var j = 0, cl = classNames.length; j < cl; j++){
16				if(classNames[j] == targetClassName){
17
18					//preload
19					preload[i] = new Image();
20					preload[i].src = images[i].getAttribute("src").replace(overReg, "$1" + suffix + "$2");
21
22					//mouseover
23					images[i].onmouseover = function() {
24						this.src = this.getAttribute("src").replace(overReg, "$1" + suffix + "$2");
25					}
26
27					//mouseout
28					images[i].onmouseout = function() {
29						this.src = this.getAttribute("src").replace(outReg, "$1$2");
30					}
31				}
32			}
33		}
34	}
35
36	function addEvent(elem,event,func){
37		if(elem.addEventListener) {
38			elem.addEventListener(event, func, false);
39		}else if(elem.attachEvent) {
40			elem.attachEvent("on" + event, func);
41		}
42	}
43	addEvent(window,"load",rollover);
44}