JS拖动效果

      function drag(o,s)
      {
        if (typeof o == "string") o = document.getElementById(o);
        o.orig_x = parseInt(o.style.left) - document.body.scrollLeft;
        o.orig_y = parseInt(o.style.top) - document.body.scrollTop;
        o.orig_index = o.style.zIndex;
		
        o.onmousedown = function(a)
        {
          this.style.cursor = "move";
          this.style.zIndex = 10000;
          var d=document;
          if(!a)a=window.event;
          var x = a.clientX+d.body.scrollLeft-o.offsetLeft;
          var y = a.clientY+d.body.scrollTop-o.offsetTop;
          d.ondragstart = "return false;"
          d.onselectstart = "return false;"
          d.onselect = "document.selection.empty();"
				
          if(o.setCapture)
            o.setCapture();
          else if(window.captureEvents)
            window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP);

          d.onmousemove = function(a)
          {
            if(!a)a=window.event;
            o.style.left = a.clientX+document.body.scrollLeft-x;
            o.style.top = a.clientY+document.body.scrollTop-y;
            o.orig_x = parseInt(o.style.left) - document.body.scrollLeft;
            o.orig_y = parseInt(o.style.top) - document.body.scrollTop;
          }

          d.onmouseup = function()
          {
            if(o.releaseCapture)
              o.releaseCapture();
            else if(window.captureEvents)
              window.captureEvents(Event.MOUSEMOVE|Event.MOUSEUP);
            d.onmousemove = null;
            d.onmouseup = null;
            d.ondragstart = null;
            d.onselectstart = null;
            d.onselect = null;
            o.style.cursor = "normal";
            o.style.zIndex = o.orig_index;
          }
        }
	
        if (s)
        {
          var orig_scroll = window.onscroll?window.onscroll:function (){};
          window.onscroll = function ()
          {
            orig_scroll();
            o.style.left = o.orig_x + document.body.scrollLeft;
            o.style.top = o.orig_y + document.body.scrollTop;
          }
        }
      }