JavaScript-拖动层

 1     //拖动 “需要给id=show的div加上绝对定位position:absolute;”
 2     window.onload = function()
 3     {
 4         var div1 = document.getElementById("show");
 5         div1.onmousedown = function(ev){
 6             var oevent = ev || event;
 7             var distanceX = oevent.clientX - div1.offsetLeft;
 8             var distanceY = oevent.clientY - div1.offsetTop;
 9         
10             document.onmousemove = function(ev){
11             var oevent = ev || event;
12             div1.style.left = oevent.clientX - distanceX + ‘px‘;
13             div1.style.top = oevent.clientY - distanceY + ‘px‘; 
14             }
15             document.onmouseup = function(){
16             document.onmousemove = null;
17             document.onmouseup = null;
18             }
19         }
20     }