Dynamic Redux Reducer - 2

createStore.js

import { createStore as _createStore, combineReducers } from 'redux';
import rootReducer from ‘./rootReducer’;

const dynamicActionGenerator = () => {
     return '@@TEST-REDUCER-VALIDITY/' + Math.random().toString(36).substring(7).split('').join('\\');
};

const isValidReducer = (reducer, throwError = false) => {
    if (typeof reducer !== 'function') {
        if (throwError) {
            throw new Error('You did not passed a valid reducer. A reducer must be a function with two parameters state and action');
        } else {
            return false;
        }
    }

    const initialState = reducer(undefined, {type: dynamicActionGenerator()});
    if (typeof initialState === 'undefined') {
        if (throwError) {
            throw new Error('Reducer must return state!!!.');
        } else {
            return false;
        }
    }
    return true;
}

const createStore = (initialReducer, initialState, enhancers) => {
    let store = _createStore(initialReducer, initialState = {}, enhancers);

    store.asyncReducers = {};
    store.attachReducer = (storeKeyPath, dynamicReducer) => {
        if (isValidReducer(dynamicReducer)) {
            store.asyncReducers = { ...store.asyncReducers, [storeKeyPath]: dynamicReducer };
        } else {
            throw new Error(`The reducer at "${storeKeyPath}" is not a valid reducer`);
        }
    };

    return store;
};

export { createStore };