freeCodeCamp/client/src/redux/createStore.js

import { createStore as reduxCreateStore, applyMiddleware } from 'redux';
import createSagaMiddleware from 'redux-saga';

import rootReducer from './rootReducer';
import rootSaga from './rootSaga';

const sagaMiddleware = createSagaMiddleware();

export const createStore = () => {
  const store = reduxCreateStore(rootReducer, applyMiddleware(sagaMiddleware));
  sagaMiddleware.run(rootSaga);
  if (module.hot) {
    // Enable Webpack hot module replacement for reducers
    module.hot.accept('./rootReducer', () => {
      const nextRootReducer = require('./rootReducer');
      store.replaceReducer(nextRootReducer);
    });
  }
  return store;
};