freeCodeCamp/common/app/create-reducer.js

import { combineReducers } from 'redux';

import { reducer as app } from './redux';
import { reducer as hikesApp } from './routes/Hikes/redux';

export default function createReducer(sideReducers = {}) {
  return combineReducers({
    ...sideReducers,
    app,
    hikesApp
  });
}