How to update a single object inside the array with useReduce on state change

I have a checkbox component and when a value is selected for a checkbox, I want to update my state with true and false values. In total I have 5 different states.I cannot update the single object from my state. Can someone help?

With the current implementation quizState becomes undefined after I set the value

My reducer looks like this:

quizState: [
    {id:0, question_id: '', answer: [] },
    {id:1, question_id: '', answer: [] },
    {id:2, question_id: '', answer: [] },
    {id:3, question_id: '', answer: [] },
    {id:4, question_id: '', answer: [] },
],

export const appReducer = (state = appState, action) => {
const { type, payload } = action;

switch (type) {
    case SET_QUIZ_STATE:
        return state.quizState.map((quiz) => quiz.id === payload.id ? ({...quiz, payload}) : quiz)

    default:
        return state;
}};

And I have a hook:

const setQuizState = useCallback(
    (quizState) => dispatch({ type: SET_QUIZ_STATE, payload: quizState }),
    [dispatch]
);

In the component, on change event:

  setQuizState({ id: 0, question_id: question.question_id, answers: [true, false] });

>Solution :

You are returning only the subfield quizState where the whole state is needed. Change your reducer like below:

export const appReducer = (state = appState, action) => {
  const { type, payload } = action;

  switch (type) {
    case SET_QUIZ_STATE:
      return {
        ...state,
        quizState: state.quizState.map(prevState => {
          if(prevState.id !== payload.id) return prevState;
          return {
            ...prevState,
            ...payload
          }
        })
      };
    default:
      return state;
  }
};

And this answer assumes that payload object is compatible to be an element in the quizState array. I think you have a typo in your onChange event where you are putting answers, not answer for your payload.