redux reducer 返回未定义处理

Question

我的减速器喜欢：

const initialState = [
  {
    fname: null,
    lname: false,
  }
]

export default function login(state = initialState, action) {
  switch (action.type) {
    case LOGIN:
      console.log("actions")
      console.log(action)
      console.log("reducers")
        return 
        [{
          fname: action.fname,
          lname: action.lname,
          }]
    default:
      return state
  }
}

在这里，我使用 fname 和 lname 获取操作对象，但这给了我错误提示 .. Uncaught Error: Reducer "login" returned undefined handling "LOGIN". To ignore an action, you must explicitly return the previous state.

为什么会出现此错误？

Answer 1

替换：

 return
 [

收件人：

 return [

因为first就像return;（js在行尾添加;）

Answer 2

或

    ...
    console.log("reducers")
            return([{
                 fname: action.fname,
                 lname: action.lname,
              }])

  //example 
  function getPerson(){
    return([{
              fname: 'jay',
              lname: 'dawg'
          }])
  }

 console.log(getPerson()[0].lname) // "dawg"

Answer 3

对我来说，发生这种情况是因为我忘记将操作调用设为异步 async

export const asyncFetchUser = () => async (dispatch) => {
  const response = *await* axios.get('http://localhost:5000/api/current_user');
  dispatch({ type: ASYNC_FETCH_USER, auth: response.data });
};

redux reducer 返回未定义处理

redux reducer returned undefined handling

reducers

redux