leaky.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Leaky page</title>
</head>
<body>

<button id='create'>Create</button>

<script>

// following code shows the   detached DOM nodes.

// here code creates ul and li nodes but not attaching it to DOM

//  A node is said to be "detached" when it's removed from the DOM tree but some JavaScript still references it

var detachedNodes;

function create() {
  var ul = document.createElement('ul');
  for (var i = 0; i < 10; i++) {
    var li = document.createElement('li');
    ul.appendChild(li);
  }
  detachedNodes = ul;
}
document.getElementById('create').addEventListener('click', create);

</script>
</body>
</html>