效果如下，有时可能会多个效果一起变化。
要点一：
box.onmouseover = function(){
startrun(box,{200,height:300},function(){
startrun(box,{opacity:100})
})
}
通过json串可以传很多值，这样就可以同时改变很多属性了。
要点二：
遍历json串中的属性值对，找出所有的属性和对应的值，计算相应的数。
并设置一个标识位，当没达到目标值时，标识位设为false，当标识位为true时，可以关闭定时器，执行下一次的调用
最后，上代码
<!DOCTYPE html>
<html>
<head>
<meta charset="gb2312" />
<title>无标题文档</title>
<style>
<!--
body{margin:0; padding:0; font:12px/1.5 arial;}
#box{width:100px; height:100px; position:absolute; background:#06c; filter:alpha(opacity=30); opacity:0.3}
-->
</style>
<script>
<!--
window.onload = function(){
var box = document.getElementById("box");
box.onmouseover = function(){
startrun(box,{200,height:300},function(){
startrun(box,{opacity:100})
})
}
box.onmouseout = function(){
startrun(box,{100,height:100},function(){
startrun(box,{opacity:30})
})
}
}
function getstyle(obj,name){
if(obj.currentStyle){
return obj.currentStyle[name];
}else{
return getComputedStyle(obj,false)[name];
}
}
function startrun(obj,json,fn){
clearInterval(obj.timer);
obj.timer = setInterval(function(){
var isall = true;
for(var attr in json){
var cur=0;
if(attr == "opacity"){
cur = Math.round(parseFloat(getstyle(obj,attr))*100);
}else{
cur = parseInt(getstyle(obj,attr));
}
var speed = (json[attr] - cur)/8
speed = speed>0?Math.ceil(speed):Math.floor(speed);
if(cur != json[attr]){
isall = false;
}
if(attr == "opacity"){
obj.style.filter = "alpha(opacity="+(cur+speed)+")";
obj.style.opacity = (cur+speed)/100;
}else{
obj.style[attr] = cur+speed+"px";
}
}
if(isall){
clearInterval(obj.timer);
if(fn){
fn();
}
}
},30);
}
//-->
</script>
</head>
<body>
<div id="box">
</div>
</body>
</html>