index.js

import React from 'react';
import ReactDOM from 'react-dom';
import {BrowserRouter} from 'react-router-dom';
import './index.css';
import App from './App';
import registerServiceWorker from './registerServiceWorker';
import {Provider} from 'react-redux';
import {createStore,applyMiddleware,compose, combineReducers} from 'redux';
import burgerBuilderReducer from './store/reducers/burgerBuilder';
import orderReducer from './store/reducers/order';
import authReducer from './store/reducers/auth';
import thunk from 'redux-thunk';

const composeEnhancers = process.env.NODE_ENV === 'development' ? window.__REDUX_DEVTOOLS_EXTENSION_COMPOSE__ : null || compose;
let rootReducer=combineReducers({burger:burgerBuilderReducer,order:orderReducer,auth:authReducer});
const store=createStore(rootReducer,composeEnhancers(applyMiddleware(thunk)));

const app=(
        <Provider store={store}>
            <BrowserRouter>
            <App />
            </BrowserRouter>    
        </Provider>
    );
ReactDOM.render( app, document.getElementById('root'));
registerServiceWorker();