核心程式碼：
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>鼠标拖动和拖拽的鼠标指针特效</title>
<style>
#box{width:100px;height:100px;background:#966;position:absolute;left:100px;top:100px;cursor:pointer;}
</style>
</head>
<body>
<div id="box"></div>
<script>
var doc=document;
function getViewport(){
return {width:Math.max(document.documentElement.clientWidth,document.documentElement.scrollWidth),
height:Math.max(document.documentElement.clientHeight,document.documentElement.scrollHeight)
};
}
function compareNum(x,minNum,maxNum){
switch(true){
case x<minNum:x=minNum;break;
case x>maxNum:x=maxNum;break;
default:x;
}
return x;
}
box.style.left='100px'
box.style.top='100px'
box.onmousedown=function(e){
var e=e||window.event;
var maxL=getViewport().width-100,
maxT=getViewport().height-100;
this.startL=parseInt(this.style.left);
this.startT=parseInt(this.style.top);
//alert(e.clientX)
this.startX=e.clientX;
this.startY=e.clientY;
//alert(maxL+':'+maxT+':'+L+':'+T)
doc.onmousemove=function(e){
posXY(e,0,0,maxL,maxT);
};
doc.onmouseup=function(){
doc.onmousemove=null;
doc.onmouseup=null;
};
return false;
}
function posXY(e,minL,minT,maxL,maxT){
var e=e||window.event;
var x=box.startL-(box.startX-e.clientX);
var y=box.startT-(box.startY-e.clientY);
box.style.left=compareNum(x,minL,maxL)+'px'
box.style.top=compareNum(y,minT,maxT)+'px'
}
</script>
</body>
</html>
