HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>length live</title>
</head>
<body>
  <div id="demo" class="card" data-role="panel">Demo</div>
  <pre id="out">Waiting...</pre>
  <script>
    var box = document.querySelector("#demo");
    var map = box.attributes;
    var before = map.length;
    box.setAttribute("title", "Demo box");
    var afterAdd = map.length;
    box.removeAttribute("class");
    var afterRemove = map.length;
    document.getElementById("out").textContent = before + " " + afterAdd + " " + afterRemove;
  </script>
</body>
</html>

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