JavaScript实现运动减速缓冲效果详解

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
<title>JavaScript运动减速效果</title>
</head>
<body>
<div style=" position:relative; border:1px solid #000000; width:550px; height:50px;">
<div id="aa" style="width:50px; height:50px; background:#930; position:absolute;"></div>
</div>
<div id="x"></div>
<div style=" position:relative; border:1px solid #000000; width:550px; height:50px;">
<div id="bb" style="width:50px; height:50px; background:#0000FF; position:absolute;"></div>
</div>
<div id="y"></div>
<script>
var $ = function (id) {
 return "string" == typeof id ? document.getElementById(id) : id;
};
var ss = 0;
var s = 500;
var tt = 300;
var a = 2*s/(tt*tt);
var o = $("aa");
var i = 0;
var t = 0;
function run(){
 t++;
 i = parseInt((a*tt)*t - .5 * a * (t*t));
 if(i>=s){ o.style.left = ss + s + "px"; return; }
 o.style.left = ss + i + "px";
 $("x").innerHTML+=i+",";
 setTimeout(run, 10);
}
run();
var s2 = 500;
var o2 = $("bb");
var i2 = 0;
function run2(){
 var s = (s2-i2)/100;
 if(s>0 && s < 1){ s=1; };
 if(s==0 || i2 + s>=s2){ o2.style.left = ss + s2 + "px"; return; }
 o2.style.left = ss + i2 + s + "px";
 i2=i2 + s;
 $("y").innerHTML+=parseInt(i2 + s)+",";
 setTimeout(run2, 10);
}
run2();
</script>
</body>
</html>