vanilla_reducers_example.js

import { combineReducers } from 'redux';

function user(state = {}, action) {
  switch (action.type) {
    case UPDATE_USERNAME:
      return {
        ...state,
        name: action.payload
      };
  }
  return state;
}

function userSettings(state = {}, action) {
  switch (action.type) {
    case UPDATE_SETTING:
      return {
        ...state,
        [action.payload.key]: action.payload.value
      };
    case RESET_SETTINGS:
      return { ...defaults };
  }
  return state;
}

export default combineReducers({ user, userSettings });