原生鼠标拖拽事件

  obj.onmousedown = function(ev){

            var ev = ev||event;

            var disX = ev.clientX - this.offsetLeft;

            var disY = ev.clientY - this.offsetTop;

             

            obj.ommousemove = function(ev){

                var ev = ev||event;

                obj.style.left = ev.clientX - disX + 'px';

                obj.style.top = ev.clientY - disY + 'px';

            }

            obj.onmouseup = function(){

                obj.onmousemove = null;

            }

        }