index.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Namaste React - Day 1</title>
</head>
<body>
  <div id="root_html">
    <h1>Namaste React using HTML</h1>
  </div>

  <div id="root_js"></div>

  <div id = "root_react"></div>

  <div id="root"></div>
  
  <script>
    /* Javascript*/
    const h1 = document.createElement("h1");
    h1.innerHTML = "Namaste React using JS";
    const root_js = document.getElementById("root_js");
    root_js.appendChild(h1);
  </script>

  <script crossorigin src="https://unpkg.com/react@18/umd/react.development.js"></script>
  <script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script>
  <script src="./app.js"></script>
</body>
</html>