function Drag(id){        var _this=this;    this.disX=0;    this.disY=0;        this.oDiv=document.getElementById(id);    this.oDiv.onmousedown=function(e)    {        _this.fnDown(e);    }}Drag.prototype.fnDown=function(e){        var _this=this;    var e=e||event;    this.disX=e.pageX-this.oDiv.offsetLeft;    this.disY=e.pageY-this.oDiv.offsetTop;    document.onmousemove=function(e)    {        _this.fnMove(e);    }    document.onmouseup=function()    {        _this.fnUp();    }}Drag.prototype.fnMove=function(e){    var e=e||event;    this.oDiv.style.left=e.pageX-this.disX+‘px‘;    this.oDiv.style.top=e.pageY-this.disY+‘px‘;}Drag.prototype.fnUp=function(){    document.onmousemove=null;    document.onmouseup=null;}function Drag2(id){    Drag.call(this,id);}for(var i in Drag.prototype){    Drag2.prototype[i]=Drag.prototype[i];}window.onload=function(){    var a = new Drag(‘div1‘);    var b = new Drag2(‘div2‘);}