                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JS动画效果

求大神帮忙看一下，看了一下午就是不知道哪里出错了，求助！！！

<!DOCTYPE html>
<html>
<head>
    <title>透明度的getSyle方法的切换</title>
    <style type="text/css">
    *{margin: 0;padding: 0;}
        ul,li{list-style: none;}
        ul li{
            width: 200px;
            height: 200px;
            background: yellow;
            filter: alpha(opacity:30);
            opacity: 0.3;
            }
    </style>
    <script type="text/javascript">
        window.onload=function(){
            var ali=document.getElementsByTagName('li');

            ali.onmouseover=function(){
                Move(this,100,'opacity');
            }
            ali.onmouseout=function(){
                Move(this,30,'opacity');
            }
        }

        function Move(obj,iTarget,attr){
            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;
                    }ele{
                        obj.style[attr]=icur+speed+'px';
                    }
                }
            },30);
        }
        function getStyle(obj,attr){
            if(obj.currentStyle){
                return obj.currentStyle[attr];
            }else{
                return getComputedStyle(obj,false)[attr];
            }
        }
    </script>
</head>
<body>
<ul>
    <li></li>
</ul>
</body>
</html>