code: function(_parent,_name){
              var _pname = _parent._$getName();
              // root not add slash child
              if (!_name&&_pname=='/'){
                  return _parent;
              }
              var _node = null;
              // check slash child first
              if (_pname!='/'){
                  _node = _parent._$getChildByName('/');
                  if (!_node){
                      _node = _t0._$$Node._$allocate();
                      _parent._$appendChild(_node);
                  }
              }
              // check non-slash child
              if (!!_name){
                  _node = _parent._$getChildByName(_name);
                  if (!_node){
                      _node = _t0._$$Node._$allocate({name:_name});
                      _parent._$appendChild(_node);
                  }
              }
              return _node;
          }
docs: build tree