title: Add class to html root
body: <p>I would like to add a class to the root html tag at the top of the page when a button is pressed. The only code I have come across is for adding classes to div elements with ids.</p>
  
  <pre><code>&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
  &lt;html class="THIS IS WHERE I WANT THE CLASS TO BE ADDED" xmlns="http://www.w3.org/1999/xhtml"&gt;
  &lt;head&gt;
  &lt;meta http-equiv="Content-Type" content="text/html; charset=utf-8" /&gt;
  &lt;title&gt;Untitled Document&lt;/title&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
  </code></pre>
  
  <p>Start presentation
      
      </p>
  
  <p>I have tried to adapt this code but nothing works ;</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  
      $("#addClass").click(function () {
  
        $('para1').addClass('presentation-started');
  
      });
  
      $("#removeClass").click(function () {
  
        $('#para1').removeClass('highlight');
  
      });
  
  &lt;/script&gt; 
  </code></pre>