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">
  <title>Hello React</title>
  <script src="https://cdn.staticfile.org/react/16.4.0/umd/react.development.js"></script>
  <script src="https://cdn.staticfile.org/react-dom/16.4.0/umd/react-dom.development.js"></script>
  <script src="https://cdn.staticfile.org/babel-standalone/6.26.0/babel.min.js"></script>
</head>

<body>
  <div id="example"></div>
  <script type="text/babel">
    var arr = [
      <h1 key="h1">Hello,</h1>,
      <h2 key="h2">React is awesome!</h2>,
    ];
    ReactDOM.render(
      <div>{ arr }</div>,
      document.getElementById('example')
    );
  </script>
</body>

</html>