index.html

<title>POPAJOPA</title>
<link rel="stylesheet" href="app.css">
<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Open+Sans:400,800">
<div id="container">
  <div id="hook"></div>
  <h1>Play Music</h1>
  <input type="file" id="files" name="files[]" multiple />
</div>
<script crossorigin src="https://unpkg.com/react@15/dist/react.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@15/dist/react-dom.js"></script>
<script src="https://npmcdn.com/babel-core@5.8.38/browser.min.js"></script>
<script src="https://soulwire.github.io/sketch.js/js/sketch.min.js"></script>
<script src="app.js"></script>
<script type="text/babel">
   function OurFirstComponent() {
    return (
      <h1>Hello, I am a React Component!</h1>
    );
  }
  const placeWeWantToPutComponent = document.getElementById('hook');
  ReactDOM.render(OurFirstComponent(), placeWeWantToPutComponent);
</script>