javascript drag sortable 拖动效果

http://6yang.net/myjavascriptlib/sortable/

for(var i = 0; i < itemlen; i++){     itemsDom[i].style.cursor = "move";     itemsDom[i].onmousedown = function(e){      var that = this,       clientRect = null,       e = tool.getEvent(e);       target = tool.getTarget(e);      while (target.nodeName.toLowerCase() !== itemsTag) {       __target = target.parentNode; //这里有点啰嗦了。:)      }      console.log(target)      doc.currentTarget = target,      clientRect = tool.getClientRect(target),　// 获取元素的位置      posArr = [e.clientX - clientRect.left, e.clientY - clientRect.top];      tool.addEvent(doc, "mousemove", fn_mousemove, false);      tool.addEvent(doc, "mouseup", fn_mouseup, false);      tool.stopEvent(e);     }    }