原生js实现div拖拽 （考虑浏览器兼容性）

参考代码：

var drag1 = document.getElementById（‘drag1’）；

drag1.onmousedown = function(ev){

   var x = ev.clientX - drag1.offsetLeft;

   var y = ev.clientY - drag1.offsetTop;

   drag1.onmousemove =  function(ev){

      drag1.style.left = ev.clientX-x+'px';

      drag1.style.top = ev.clientY-y + 'px';

   }

  drag1.onmouseup = function ( ev ) {

  drag1.onmousemove=drag1.onmouseup=null;

  }

}

前提是：要给div设置有定位属性position