base库插件---拖动

 /**
  * Created by Administrator on 2014/6/5 0005.  Base-drag 基于Base库的拖拽插件  tags为你要拖拽的元素参数， 数组形式传入
  */
 
 $().extend('drag', function () {
     var tags = arguments;
     for (var i = 0; i < this.elements.length; i ++) {
         addEvent(this.elements[i], 'mousedown', function (e) {
             if (trim(this.innerHTML).length == 0) e.preventDefault();
             var _this = this;
             var diffX = e.clientX - _this.offsetLeft;
             var diffY = e.clientY - _this.offsetTop;
 
             //自定义拖拽区域
             var flag = false;
 
             for (var i = 0; i < tags.length; i ++) {
                 if (e.target == tags[i]) {
                     flag = true;                    //只要有一个是true，就立刻返回
                     break;
                 }
             }
 
             if (flag) {
                 addEvent(document, 'mousemove', move);
                 addEvent(document, 'mouseup', up);
             } else {
                 removeEvent(document, 'mousemove', move);
                 removeEvent(document, 'mouseup', up);
             }
 
             function move(e) {
                 var left = e.clientX - diffX;
                 var top = e.clientY - diffY;
 
                 if (left < 0) {
                     left = 0;
                 } else if (left <= getScroll().left) {
                     left = getScroll().left;
                 } else if (left > getInner().width + getScroll().left - _this.offsetWidth) {
                     left = getInner().width + getScroll().left - _this.offsetWidth;
                 }
 
                 if (top < 0) {
                     top = 0;
                 } else if (top <= getScroll().top) {
                     top = getScroll().top;
                 } else if (top > getInner().height + getScroll().top - _this.offsetHeight) {
                     top = getInner().height + getScroll().top - _this.offsetHeight;
                 }
 
                 _this.style.left = left + 'px';
                 _this.style.top = top + 'px';
 
                 if (typeof _this.setCapture != 'undefined') {
                     _this.setCapture();
                 }
             }
 
             function up() {
                 removeEvent(document, 'mousemove', move);
                 removeEvent(document, 'mouseup', up);
                 if (typeof _this.releaseCapture != 'undefined') {
                     _this.releaseCapture();
                 }
             }
         });
     }
     return this;
 });