HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>insertAdjacentElement beforebegin</title>
  <style>
    .banner { background: #fff3cd; padding: 8px; border: 1px solid #e0c200; }
    .card { padding: 12px; border: 1px solid #333; margin-top: 8px; }
  </style>
</head>
<body>
  <div id="card" class="card">Card content</div>
  <button type="button" id="btn">Insert banner before</button>
  <pre id="out">—</pre>
  <script>
    var card = document.getElementById("card");
    document.getElementById("btn").onclick = function () {
      var banner = document.createElement("div");
      banner.className = "banner";
      banner.textContent = "New banner";
      card.insertAdjacentElement("beforebegin", banner);
      document.getElementById("out").textContent =
        "previous sibling: " + (card.previousElementSibling && card.previousElementSibling.className);
    };
  </script>
</body>
</html>

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Element.insertAdjacentElement — beforebegin sibling (Try It)