reactjs/helloworld_batman.htm

<!DOCTYPE html>
<html>

<head>
  <meta charset="UTF-8" />
  <title>React! React! React!</title>
  <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 src="https://unpkg.com/babel-standalone@6.15.0/babel.min.js"></script>

  <style>
    #container {
      padding: 50px;
      background-color: #EEE;
    }
    #container h1 {
      font-size: 144px;
      font-family: sans-serif;
      color: #0080a8;
    }
  </style>
</head>

<body>
  <div id="container"></div>

  <script type="text/babel">
    var destination = document.querySelector("#container");

    ReactDOM.render(
      <h1>Batman</h1>,
      destination
    );   
  </script>
</body>

</html>