code: function(targets, targetBoxMapper, judge) {
                  var sourceBoxes = this._dragSources.map(function(source) {
                      return source.getLayoutBox();
                  });
                  var i, j, target, sourceBox, targetBox;
                  judge = judge || function(intersectBox, sourceBox, targetBox) {
                      return intersectBox && !intersectBox.isEmpty();
                  };
                  for (i = 0; i < targets.length; i++) {
                      target = targets[i];
                      targetBox = targetBoxMapper.call(this, target, i);
                      for (j = 0; j < sourceBoxes.length; j++) {
                          sourceBox = sourceBoxes[j];
                          var intersectBox = sourceBox.intersect(targetBox);
                          if (judge(intersectBox, sourceBox, targetBox)) {
                              return target;
                          }
                      }
                  }
                  return null;
              }
docs: 通过 judge 函数判断 targetBox 和 sourceBox 的位置交叉关系
  @param targets -- 目标节点
  @param targetBoxMapper -- 目标节点与对应 Box 的映射关系
  @param judge -- 判断函数
  @returns {*}
  @private