Edit in JSFiddle

  <body>
    <div id="content"></div>
    <script type="text/babel">
      // tutorial1.js
var CommentBox = React.createClass({
  render: function() {
    return (
      <div className="commentBox">
        Hello, world! I am a CommentBox.
      </div>
    );
  }
});
ReactDOM.render(
  <CommentBox />,
  document.getElementById('content')
);
    </script>
  </body>