JavaScript实现颜色动态淡化效果

<html>
<head>
<title>颜色变换</title>
<style type="text/css">
div{width:100px;height:100px;margin:100px auto;border:1px solid white;border-radius:50%;}
input{position:absolute;left:100px;top:100px;}
</style>
</head>
<body>
<input type="button" value="点击执行颜色淡化效果"/>
<script type="text/javascript">
var a=255,b=165,c=0,w=100,box;
function cont()
{
a=255;
b=165;
c=0;
w=100;
box = document.createElement('div');
document.body.appendChild(box);
}
function changeColor()
{
document.getElementsByTagName('input')[0].disabled="disabled";
box.style.backgroundColor="RGB("+a+","+b+","+c+")";
box.style.width=w;
box.style.height=w;
c++;
if(c>=166)b++;
w++;
if(a>=255&&b>255&&c>255)
{
box.parentNode.removeChild(box);
document.getElementsByTagName('input')[0].removeAttribute('disabled');
return false;
}
setTimeout(changeColor,1);
}
document.getElementsByTagName('input')[0].onclick=function()
{
cont();
changeColor();
}
</script>
</body>
</html>