該實例可實現(xiàn)鼠標移上，先寬度變化，再高度變化，最后透明度變化，鼠標移出，再依次變回去的效果。
要點一：
startrun(obj,attr,target,fn)
box.onmouseover = function(){
startrun(box,"width",200,function(){
startrun(box,"height",200,function(){
startrun(box,"opacity","100")
});
});
}
如上面，函數(shù)也可以做為參數(shù)使用，就可以達到先執(zhí)行某個動作，再執(zhí)行某個動作的效果了。
要點二：
if(cur == target){
clearInterval(obj.timer);
if(fn){
fn();
}
}
當運動到達目標點，關閉定時器，然后就可以執(zhí)行新的函數(shù)了。
最后，上代碼：
<!DOCTYPE html>
<html>
<head>
<meta charset="gb2312" />
<title>無標題文檔</title>
<style>
<!--
body{margin:0; padding:0; font:12px/1.5 arial;}
#box{width:100px; height:100px; position:absolute;
background:#06c; left:0;filter:alpha(opacity=30); opacity:0.3;}
-->
</style>
<script>
<!--
function getstyle(obj,name){
if(obj.currentStyle){
return obj.currentStyle[name];
}else{
return getComputedStyle(obj,false)[name];
}
}
window.onload = function(){
var box = document.getElementById("box");
box.onmouseover = function(){
startrun(box,"width",200,function(){
startrun(box,"height",200,function(){
startrun(box,"opacity","100")
});
});
}
box.onmouseout = function(){
startrun(box,"height",100,function(){
startrun(box,"width",100,function(){
startrun(box,"opacity","30");
});
});
}
}
function startrun(obj,attr,target,fn){
clearInterval(obj.timer);
obj.timer = setInterval(function(){
var cur = 0;
if(attr == "opacity"){
cur = Math.round(parseFloat(getstyle(obj,attr))*100);
}else{
cur = parseInt(getstyle(obj,attr));
}
var speed = (target-cur)/8;
speed = speed>0?Math.ceil(speed):Math.floor(speed);
if(cur == target){
clearInterval(obj.timer);
if(fn){
fn();
}
}else{
if(attr == "opacity"){
obj.style.filter = "alpha(opacity="+(cur+speed)+")";
obj.style.opacity = (cur+speed)/100;
}else{
obj.style[attr] = cur + speed + "px";
}
}
},30)
}
//-->
</script>
</head>
<body>
<div id="box">
</div>
</body>
</html>
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