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>

希望本文所述對大家的javascript程序設計有所幫助。

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