code: function(_smap,_new,_key,_dmap){
              var _old = _smap[_key];
              if (_u._$isFunction(_new)&&
                  _u._$isFunction(_old)){
                  _smap[_key] = _old._$aop(_new);
                  return;
              }
              _smap[_key] = _new;
          }
docs: merge extend