我照着老师写的为什么没有效果
#box {width:200px;height:200px;opacity:0.3;margin:0 auto;background-color:#F00;}
</style>
<script type=text/javascript>
window.onload=function(){
var bo1=document.getElementById(box);
bo1.onmouseover=function(){
boc(100);
}
bo1.onmouseout=function(){
boc(30);}
}
var timer=null;
var va=30;
function boc(ita)
{
clearInterval(timer);
var bo1=document.getElementById(box);
timer=setInterval(function(){
var speed=0;
if (va>ita)
{
speed=-10;}
else
{
speed=10;}
if (va==ita)
{
clearInterval(timer);
}
else{
va+=speed;
bo1.style.opacity=va/100;
}},30)
}
</script>
