code: function () {
                                      itemOld = slot.item;
  
                                      slot.itemNew = {
                                          key: key,
                                          data: newData
                                      };
  
                                      if (itemOld) {
                                          changeSlot(slot);
                                      } else {
                                          completeFetchPromises(slot);
                                      }
                                  }
docs: updateSlots