import { createStore, applyMiddleware, combineReducers, compose } from 'redux';
import { asyncStoreCreator } from 'async-redux-store-enhancer'
 
// instead of passing a reducer to createStore, we pass a reducer factory
// where the only difference from normal reducer is that it takes an argument of new reducers and spreads it.
const createReducer = (newReducers = {}) => combineReducers({
  yourReducers,
  ...newReducers,
})
 
// this creates your usual redux store, that has 2 additional methods:
// injectReducer(reducerName, reducerFunction)
// injectMiddleware(middlewareFunction)
const store = asyncStoreCreator(createStore, applyMiddleware, compose)(createReducer, initialState, middleware);
 
store.injectReducer('newReducer', newReducerFunction); // that's it this adds new reducer, while preserving previous state
store.injectMiddleware(newMiddlewareFunction); // adding new middleware is as easy as this, this new middleware function will be called after all other are called

// you can pass 4th argument { prependNewMiddleware } to the store creator factory
const store = asyncStoreCreator(createStore, applyMiddleware, compose, { prependNewMiddleware: true })(createReducer, initialState, middleware);

import { createStore, applyMiddleware, combineReducers, compose } from 'redux';
import { asyncStoreCreator } from 'async-redux-store-enhancer'
 
// as per redux dev tools documentation
const composeEnhancers = window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ || compose;
 
const store = asyncStoreCreator(createStore, applyMiddleware, composeEnhancers)(createReducer);