리액트 리덕스 에러해결 Error: Reducer "user" returned undefined during initialization. If the state passed to the reducened. If you don't want to set a value for this reducer, you can use null instead of undefined.

Error: Reducer "user" returned undefined during initialization. If the state passed to the reducened. If you don't want to set a value for this reducer, you can use null instead of undefined.

이러한 에러가 발생했을 경우,

이렇게 user의 초기상태를 선언해 줘야 한다.

const initialState = {
  user: {
    isLoggingIn: true,
    data: null,
  },
  posts: [],
};