code: function(another) {
                  if (this.isEmpty()) {
                      return new Box(another.x, another.y, another.width, another.height);
                  }
                  var left = Math.min(this.left, another.left), right = Math.max(this.right, another.right), top = Math.min(this.top, another.top), bottom = Math.max(this.bottom, another.bottom);
                  return new Box(left, top, right - left, bottom - top);
              }
docs: @method merge()
  @for kity.Box
  @description 把当前矩形区域和指定的矩形区域合并，返回一个新的矩形区域（即包含两个源矩形区域的最小矩形区域）
  
  @grammar merge(another) => {kity.Box}
  @param  {kity.Box} another 要合并的矩形区域
  
  @example
  
  ```js
  var box1 = new kity.Box(10, 10, 50, 50);
  var box2 = new kity.Box(30, 30, 50, 50);
  var box3 = box1.merge(box2);
  console.log(box3.valueOf()); // [10, 10, 70, 70]
  ```