reduxReducer.js

const reducer = (state, action) => {
  switch (action.type) {
    case FETCH_DATA: {
      return {
        ...state,
        isFetching: true
      }
    }
    case FETCH_DATA_SUCCESS: {
      return {
        ...state,
        isFetching: false,
        data: action.payload
      }
    }
    default: {
      return state
    }
  }