JS实现拖拽效果

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>拖拽效果</title>
<style>
#div1 {width:200px; height:200px; background:blue; position:absolute;}
</style>
<script>
window.onload=function ()
{
    var oDiv=document.getElementById('div1');
    
    oDiv.onmousedown=function (ev)
    {
        var oEvent=ev||event;
        
        var disX=oEvent.clientX-oDiv.offsetLeft;
        var disY=oEvent.clientY-oDiv.offsetTop;
        
        document.onmousemove=function (ev)
        {
            var oEvent=ev||event;
            
            oDiv.style.left=oEvent.clientX-disX+'px';
            oDiv.style.top=oEvent.clientY-disY+'px';
        };
        
        document.onmouseup=function ()
        {
            document.onmousemove=null;
            document.onmouseup=null;
        };
    };
};
</script>
</head>
<body>
<div ></div>
</body>
</html>
链接：Markdown 编辑器语法指南