Reset all reducers back to their initial states when user logout

rootReducer.js

import {combineReducers} from 'redux';
import { LOGOUT } from '../common/constants';
import { UnauthorizedErrorReducer } from '../common/commonReducers';
import FirstReducer from './FirstReducer';
import SecondReducer from './SecondReducer';
import ThirdReducer from './ThirdReducer';

/* In order to reset all reducers back to their initial states when user logout,
 * rewrite rootReducer to assign 'undefined' to state when logout
 *
 * If state passed to reducer is 'undefined', then the next state reducer returns
 * will be its initial state instead; since we have assigned it as the default value
 * of reducer's state parameter
 *   ex: const Reducer = (state = InitialState, action) => { ... }
 *
 * See: https://goo.gl/GSJ98M and combineReducers() source codes for details
 */
const appReducer = combineReducers({
  unauthorized: UnauthorizedErrorReducer,
  first: FirstReducer,
  second: SecondReducer,
  third: ThirdReducer,
});

export default rootReducer = (state, action) => {
  if (action.type === LOGOUT) {
    state = undefined;
  }

  return appReducer(state, action);
};