最精简的JavaScript鼠标拖动代码

var drag_=false
var D=new Function('obj','return document.getElementById(obj);')
var oevent=new Function('e','if (!e) e = window.event;return e')
function Move_obj(obj){
    var x,y;
    D(obj).onmousedown=function(e){
        drag_=true;
        with(this){
            style.position="absolute";var temp1=offsetLeft;var temp2=offsetTop;
            x=oevent(e).clientX;y=oevent(e).clientY;
            document.onmousemove=function(e){
                if(!drag_)return false;
                with(this){
                    style.left=temp1+oevent(e).clientX-x+"px";
                    style.top=temp2+oevent(e).clientY-y+"px";
                }
            }
        }
        document.onmouseup=new Function("drag_=false");
    }
}