JavaScript 智能社拖拽

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
#div1 {100px; height:100px; background:red; position:absolute;}
#div2 {400px; height:300px; background:#CCC; position:relative;}
</style>
<script>
window.onload=function ()
{
    var oDiv=document.getElementById('div1');
    var oDiv2=document.getElementById('div2');
    
    var disX=0;
    var disY=0;
    
    oDiv.onmousedown=function (ev)
    {
        var oEvent=ev||event;
        
        disX=oEvent.clientX-oDiv.offsetLeft;
        disY=oEvent.clientY-oDiv.offsetTop;
        
        document.onmousemove=function (ev)
        {
            var oEvent=ev||event;
            var l=oEvent.clientX-disX;
            var t=oEvent.clientY-disY;
            
            if(l<0)
            {
                l=0;
            }
            else if(l>oDiv2.offsetWidth-oDiv.offsetWidth)
            {
                l=oDiv2.offsetWidth-oDiv.offsetWidth;
            }
            
            if(t<0)
            {
                t=0;
            }
            else if(t>oDiv2.offsetHeight-oDiv.offsetHeight)
            {
                t=oDiv2.offsetHeight-oDiv.offsetHeight;
            }
            
            oDiv.style.left=l+'px';
            oDiv.style.top=t+'px';
        };
        
        document.onmouseup=function ()
        {
            document.onmousemove=null;
            document.onmouseup=null;
        };
        
        return false;
    };
};
</script>
</head>

<body>
<div id="div2">
    <div id="div1"></div>
</div>
</body>
</html>
JavaScript 智能社 拖拽

JavaScript 智能社拖拽
