UsersReducer.js

const defaultState = {
    user: {}
};

export default function reducer(state, action) {
    state = state || defaultState;
    const { type, payload } = action;
    
    switch (type) {
        case 'SET_USER_DETAILS': 
            return {
                ...state,
                user: payload.user
            };
        
        default:
            return state;
    }
}