title: Argument 1 of Node.appendChild does not implement interface Node
body: <p>I am new to JavaScript, and i cannot figure out what are interface nodes? Below is my code with the error</p>
  
  <pre><code>Panel = function () {
     var popUpDiv = document.getElementById("firewall-content");
     var panelDiv = $("&lt;div&gt;&lt;/div&gt;").addClass("side_panel");
     popUpDiv.appendChild(panelDiv);
  };
  </code></pre>