Reducer的初始化状态中有两个布尔值状态，其中一个返回未定义

const initialState = {
  isLoading: false,
  isError: false
};

const rootReducer = (state = initialState, action) => {
  switch (action.type) {
    case 'START_LOADING':
      return { ...state, isLoading: true };
    case 'STOP_LOADING':
      return { ...state, isLoading: false };
    case 'SET_ERROR':
      return { ...state, isError: true };
    case 'CLEAR_ERROR':
      return { ...state, isError: false };
    default:
      return state;
  }
};

const rootReducer = (state = initialState, action) => {
  switch (action.type) {
    case 'START_LOADING':
      return { ...state, isLoading: true };
    case 'STOP_LOADING':
      return { ...state, isLoading: false };
    case 'SET_ERROR':
      return { ...state, isError: true };
    case 'CLEAR_ERROR':
      return { ...state, isError: false };
    default:
      return state; // 确保默认情况下返回初始状态
  }
};

// 初始状态
const initialState = {
  isLoading: false,
  isError: false
};

// Reducer
const rootReducer = (state = initialState, action) => {
  switch (action.type) {
    case 'START_LOADING':
      return { ...state, isLoading: true };
    case 'STOP_LOADING':
      return { ...state, isLoading: false };
    case 'SET_ERROR':
      return { ...state, isError: true };
    case 'CLEAR_ERROR':
      return { ...state, isError: false };
    default:
      return state;
  }
};

// 创建store
const store = createStore(rootReducer);

// 示例动作
const startLoadingAction = { type: 'START_LOADING' };
const stopLoadingAction = { type: 'STOP_LOADING' };
const setErrorAction = { type: 'SET_ERROR' };
const clearErrorAction = { type: 'CLEAR_ERROR' };

// 分发动作
store.dispatch(startLoadingAction);
console.log(store.getState()); // { isLoading: true, isError: false }

store.dispatch(stopLoadingAction);
console.log(store.getState()); // { isLoading: false, isError: false }

store.dispatch(setErrorAction);
console.log(store.getState()); // { isLoading: false, isError: true }

store.dispatch(clearErrorAction);
console.log(store.getState()); // { isLoading: false, isError: false }