Put this in your Reducers folder and include it in your root reducer with combineReducers();

errorsReducer.jsx

import { RECEIVE_ERRORS, CLEAR_ERRORS } from '../actions/errorActionCreators';
// Note: Unlike in other reducers, errors are stored in a simple array
const defaultState = () => [];
const ErrorsReducer = (state = defaultState(), action) => {
  Object.freeze(state);
  switch (action.type) {
    case RECEIVE_ERRORS:
      return action.errors;
    case CLEAR_ERRORS:
      return [];
    default:
      return state;
  }
};
export default ErrorsReducer;