HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>new null</title>
</head>
<body>
  <div id="demo" class="card">Demo</div>
  <pre id="out">Waiting...</pre>
  <script>
    var box = document.querySelector("#demo");
    var role = document.createAttribute("data-role");
    role.value = "panel";
    var replaced = box.attributes.setNamedItem(role);
    document.getElementById("out").textContent = String(replaced === null) + " " + box.getAttribute("data-role");
  </script>
</body>
</html>

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NamedNodeMap.setNamedItem() — new attr null (Try It)