js实现完美拖拽效果可拖动层与回放拖动规迹并显示拖动距离参数

<!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=utf-8" /> 
<title>完美拖拽</title> 
<style type="text/css"> 
html,body{overflow:hidden;} 
body,div,h2,p{margin:0;padding:0;} 
body{color:#fff;background:#000;font:12px/2 Arial;} 
p{padding:0 10px;margin-top:10px;} 
span{color:#ff0;padding-left:5px;} 
#box{position:absolute;width:300px;height:150px;background:#333;border:2px solid #ccc;top:50%;left:50%;margin:-75px 0 0 -150px;} 
#box h2{height:25px;cursor:move;background:#222;border-bottom:2px solid #ccc;text-align:right;padding:0 10px;} 
#box h2 a{color:#fff;font:12px/25px Arial;text-decoration:none;outline:none;} 
</style> 
<script type="text/javascript"> 
window.onload=function () 
{ 
var oBox=document.getElementById("box"); 
var oH2 = oBox.getElementsByTagName("h2")[0]; 
var oA = oBox.getElementsByTagName("a")[0]; 
var aSpan = oBox.getElementsByTagName("span"); 
var disX = disY = 0; 
var bDrag = false; 
var aPos = [{x:oBox.offsetLeft, y:oBox.offsetTop}] 
//鼠标按下, 激活拖拽 
oH2.onmousedown = function (event) 
{ 
var event = event || window.event; 
bDrag = true; 
disX = event.clientX - oBox.offsetLeft; 
disY = event.clientY - oBox.offsetTop; 
aPos.push({x:oBox.offsetLeft, y:oBox.offsetTop}) 
this.setCapture && this.setCapture(); 
return false 
};

//拖拽开始 
document.onmousemove = function (event) 
{ 
if (!bDrag) return; 
var event = event || window.event; 
var iL = event.clientX - disX; 
var iT = event.clientY - disY; 
var maxL = document.documentElement.clientWidth - oBox.offsetWidth; 
var maxT = document.documentElement.clientHeight - oBox.offsetHeight; 
iL = iL < 0 ? 0 : iL; 
iL = iL > maxL ? maxL : iL;

iT = iT < 0 ? 0 : iT; 
iT = iT > maxT ? maxT : iT; 
oBox.style.marginTop = oBox.style.marginLeft = 0; 
oBox.style.left = iL + "px"; 
oBox.style.top = iT + "px"; 
aPos.push({x:iL, y:iT}) 
status(); 
return false 
}; 
//鼠标释放, 结束拖拽 
document.onmouseup = window.onblur = oH2.onlosecapture = function () 
{ 
bDrag = false; 
oH2.releaseCapture && oH2.releaseCapture(); 
status() 
};

//回放拖动轨迹 
oA.onclick = function () 
{ 
if (aPos.length == 1) return; 
var timer = setInterval(function () 
{ 
var oPos = aPos.pop(); 
oPos ? (oBox.style.left = oPos.x + "px", oBox.style.top = oPos.y + "px", status()) : clearInterval(timer) 
}, 30);

this.focus = false;//去除链接虚线

return false 
};

//阻止冒泡 
oA.onmousedown = function (event) 
{ 
(event || window.event).cancelBubble = true 
};

//监听状态函数 
function status () 
{ 
aSpan[0].innerHTML = bDrag; 
aSpan[1].innerHTML = oBox.offsetTop; 
aSpan[2].innerHTML = oBox.offsetLeft 
}

//初始调用 
status() 
}; 
</script> 
</head> 
<body> 
 
<h2>点击回放拖动轨迹</h2> 
<p><strong>Drag:</strong><span></span></p> 
<p><strong>offsetTop:</strong><span></span></p> 
<p><strong>offsetLeft:</strong><span></span></p> 
 
</body> 
</html>

[Ctrl+A 全选注:如需引入外部Js需刷新才能执行]