为什么我的任意属性值（二）中的这个代码不运行？
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>任意属性值运动2</title>
<style>
* {
margin: 0;
padding: 0;
}
ul,li{
list-style: none;
}
ul li {
width: 200px;
height: 100px;
background:yellow;
margin-bottom: 20px;
border: 4px solid #000;
filter:alpha(opacity=30);
opacity:0.3;
}
</style>
</head>
<body>
<ul>
<li id="li1"></li>
</ul>
<script>
window.onload=function(){
/*var aLi = document.getElementsByTagName('li');
for(var i=0;i<aLi.length;i++){
aLi.timer = null;
aLi[i].onmouseover = function(){
startMove(this,400);
}
aLi[i].onmouseout = function(){
startMove(this,200);
}
}*/
var Li1=document.getElementById('li1');
Li1.onmouseover=function(){
startMove(this,'opacity',100);
}
Li1.onmouseout=function(){
startMove(this,'opacity',30);
}
}
function getStyle(obj,attr){
if(obj.currentStyle){
return obj.currentStyle[attr];
}else{
return getComputedStyle(obj,false)[attr];
}
}
//var timer = null;
var alpha = 30;
function startMove(obj,attr,iTarget){
clearInterval(obj.timer);
obj.timer=setInterval(function(){
var icur = 0;
if(attr == 'opacity'){
icur = parseFloat(getStyle(obj.attr))*100;
}else{
icur=parseInt(getStyle(obj,attr));
}
var speed=(iTarget-icur)/8;
speed=speed>0?Math.ceil(speed):Math.floor(speed);
if(icur==iTarget){
clearInterval(obj.timer);
}else{
if(attr == 'opacity'){
obj.style.filter = 'alpha(opacity:'+(icur + speed)+')'
obj.style.opacity = (icur + speed)/100;
}else{
obj.style[attr]=icur+speed+'px';
}
}
},30);
}
</script>
</body>
</html>
为什么我这个不运行？我改成HEIGHT可以运行，但是透明度却不可以，我都照着老师的抄了，为什么会这样呢?
