HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>insertAdjacentHTML afterbegin</title>
  <style>.banner { background: #fff3cd; padding: 8px; border: 1px solid #e0c200; }</style>
</head>
<body>
  <div id="panel"><p>Panel content</p></div>
  <button type="button" id="btn">Add banner</button>
  <pre id="out">—</pre>
  <script>
    document.getElementById("btn").onclick = function () {
      var panel = document.getElementById("panel");
      panel.insertAdjacentHTML("afterbegin", '<div class="banner">New notice</div>');
      document.getElementById("out").textContent = panel.firstElementChild.className;
    };
  </script>
</body>
</html>

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Element.insertAdjacentHTML — afterbegin banner (Try It)