javascript動畫效果類封裝代碼

<input id=output3 style="position:absolute;top:300;left:300;"/>
<input id=output1 />
<input id=output2 />
<br/>
<input id=output4 />

<script>
function Animation(target,targetProperty,closure,precision)
{
closure=closure||function(x){return x;};
precision=precision||10;
this.handle;

var beginTime=new Date();
var stopTime=new Date();
this.Begin=function(){
beginTime=new Date();
this.handle=setInterval(
function(){
var now=new Date();
target[targetProperty]=closure(now.getTime()-beginTime.getTime());
},
precision
);
}

this.Continue=function(){
var now=new Date();
beginTime.setTime(now.getTime()-stopTime.getTime()+beginTime.getTime());

this.handle=setInterval(
function(){
var now=new Date();
target[targetProperty]=closure(now.getTime()-beginTime.getTime());
},
precision
);
}

this.Stop=function(duration){

clearInterval(this.handle);

if(duration===undefined)
{
stopTime=new Date();
duration=stopTime.getTime()-beginTime.getTime();
}
else stopTime.setTime(beginTime.getTime()+duration)
target[targetProperty]=closure(duration);
}
}

function StoryBoard(Duration,onfinish,flag)
{
onfinish=onfinish||function(){};
var r=new Array();
r.appendAnimation=function(animation)
{
if(animation instanceof Animation)
this.push(animation);
}
r.removeAnimation=function(animation)
{
for(var i=0;i<r.length;i++)
{
if(r[i]==animation)
{
r.splice(i,1);
break;
}
}
}
r.start=function(){
for(var i=0;i<r.length;i++)
{
r[i].Begin();
}
setTimeout(
function(){
for(var i=0;i<r.length;i++)
{
r[i].Stop(Duration);
}
},
Duration
);
onfinish();
}
return r;

}
//////////////////////////////下面是使用方法////////////////////////////////
function $(id)
{
return document.getElementById(id);
}
var a1=new Animation($("output1"),"value");
var a2=new Animation($("output2"),"width",function(x){return Math.floor(x/10);});
var a3=new Animation($("output3").style,"filter",function(x){return "alpha(opacity="+Math.floor(x/5000*100)+")";});
var a4=new Animation($("output4").style,"width",function(x){return Math.floor(x*x*x/50000/5000)+"px";});
var s=new StoryBoard(5000);
s.appendAnimation(a1);
s.appendAnimation(a2);
s.appendAnimation(a3);
s.appendAnimation(a4);
s.start();

</script>
<pre>
output1是改變value
output1是改變寬度
output3是淡入
output4是帶緩動的寬度
</pre>