index.html

<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <script crossorigin src="https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.26.0/babel.min.js"></script>
  <script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
  <script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
  <script crossorigin src="https://cdnjs.cloudflare.com/ajax/libs/redux/4.0.0/redux.min.js"></script>
  <script crossorigin src="https://cdnjs.cloudflare.com/ajax/libs/react-redux/5.0.7/react-redux.min.js"></script>
  <title>React Playground</title>
</head>

<body>
  <div id="react-app"></div>
  <script type="text/babel" src="store/reducers/foo.reducer.js"></script>
  <script type="text/babel" src="store/index.js"></script>
  <script type="text/babel" src="components/Main.jsx"></script>
  <script type="text/babel" src="components/Message.jsx"></script>
  <script type="text/babel" src="app.jsx"></script>
</body>

</html>