title: Add a class to a-tag with specific ID-link
body: <p>I am trying to add the CSS-Class "active" to the anchor-tag which has a href-attribute containing the ID which is currently active in the URL. This is my code so far, but I can't get window.location.hash to work.</p>
  
  <pre><code>$( "a[href="window.location.hash"]" ).addClass('active');
  </code></pre>
  
  <p>I need your help!</p>
  
  <p>Additionaly I have to remove that class if the "window.location.hash" changes! I forgot about that :(</p>