redux_dependency.js

// dependency - you need to finish load rooms before you load reservations

let roomsLoadPromise = undefined;

export function loadRooms() {
  return async function (dispatch, getState) {
    if (!roomsLoadPromise) {
      roomsLoadPromise = dispatch(_loadRooms());
    }
    await roomsLoadPromise;
  };
}

function _loadRooms() {
  return async function (dispatch, getState) {
    dispatch({type: types.ROOMS_LOADING});
    const rooms = await hotelService.loadRooms();
    dispatch({type: types.ROOMS_LOADED, rooms: rooms});
  };
}

export function loadReservations() {
  return async function (dispatch, getState) {
    await dispatch(loadRooms());
    dispatch({type: types.RESERVATIONS_LOADING});
    const reservations = await hotelService.loadReservations();
    dispatch({type: types.RESERVATIONS_LOADED, reservations: reservations});
  };
}