我按照老师的视频敲的代码怎么实现不了透明度渐变，哪位大神帮忙看下，谢谢！
<script type="text/javascript">
window.onload+function(){
var odiv=document.getElementById("div1");
odiv.onmouseover=function(){
starMove(100);
};
odiv.onmouseout=function(){
starMove(30);
};
};
var timer=null;
var alpha=30;
function starMove(morm){
var odiv=document.getElementById("div1");
clearInterval(timer);
timer=setInterval(function(){
var speed=0;
if (speed>morm) {
speed=-10;
} else{
speed=10;
};
if(alpha==morm){
clearInterval(timer);
}else{
alpha+=speed;
odiv.style.filter="alpha(opactiy:"+alpha+")";
odiv.style.opacity=alpha/100;
};
},30);
};
</script>
