title: Check if element contains another one in jQuery
body: <p>I found many related things on Stack Overflow but not applicable for my case.</p>
  
  <p>It's all in this exemple, I need to check if an element contains another one, and if yes, append something.</p>
  
  <pre><code>$(".bt_repondre").click(function(){
      comment = $(this).parent().parent().parent();
      //I want to check if comment contains a .comment_full element, if no, append.
      comment.append('add');
  });
  </code></pre>
  
  <p>Hope you can help me, I tried so many things...</p>