redux dev tools with applyMiddleware using compose

main.js

import React, { Component, PropTypes } from 'react'
import { render } from 'react-dom'
import { applyMiddleware, combineReducers, createStore, compose } from 'redux'
import { Provider, connect } from 'react-redux'
import thunk from 'redux-thunk'
import { Router, Route, Link, IndexRoute, browserHistory } from 'react-router'

let enhancer = applyMiddleware(thunk);
const hasReduxDevTools = !!window.devToolsExtension;
if (hasReduxDevTools) {
  enhancer = compose(enhancer, window.devToolsExtension());
}

const rootReducer = (state = 0, action) => state;
const store = createStore(rootReducer, enhancer);

const Layout = (props) =>
  <div id="app">{props.children}</div>

const App = () =>
  <h1>Hello World!</h1>

const Main = () =>
  <Provider store={store}>
    <Router history={browserHistory}>
      <Route path="/" component={Layout}>
        <IndexRoute component={App} />
      </Route>
    </Router>
  </Provider>

render(<Main />, document.getElementById('app'))