redux dev tool extension

index.js

import {createStore} from 'redux'
import rootReducer from './reducers'
import {Provider} from 'react-redux'

const store = createStore(
    rootReducer,
    window.__REDUX_DEVTOOLS_EXTENSION__ && window.__REDUX_DEVTOOLS_EXTENSION__() 
)

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