redux counter in es6

app.js

import React from 'react'
import ReactDOM from 'react-dom'
import { createStore } from 'redux'

const INCREMENT = 'INCREMENT'
const DECREMENT = 'DECREMENT'

const reducer = (state = 0, action) => {
  switch (action.type) {
    case INCREMENT:
      return state + 1
    case DECREMENT:
      return state - 1
    default:
      return state
  }
}

const store = createStore(reducer)

const Counter = ({value}) =>
  <div>
    <button onClick={() => store.dispatch({ type: DECREMENT })}>-</button>
    <span>{value}</span>
    <button onClick={() => store.dispatch({ type: INCREMENT })}>+</button>
  </div>

const appContainer = document.getElementById('app')
const render = () =>
  ReactDOM.render(
    <Counter value={store.getState()} />,
    appContainer
  )
  
store.subscribe(render)
render()