protoMerge_reducer.js

function usersReducer(state, action) {
  switch (action.type) {
    case CHANGE_NAME:
      const { id, name } = action.payload;
      return {
        byId: {
          ...state.byId,
          [id]: {
            ...state.byId[id],
            name: name,
          }
        }
        allIds: state.allIds,
      };
    default:
      return state;
  }
}