title: jQuery selector for a specific li
body: <p>I have the following markup </p>
  
  <pre><code>&lt;div id="search-query-autocomplete"&gt;
    &lt;ul id="autocomplete-results"&gt;
      &lt;li class="auto-li"&gt;blue&lt;/li&gt;
    &lt;/ul&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and want to add a class to the first auto-li when the user keys down. </p>
  
  <p>I have the following javascript:</p>
  
  <pre><code>document.onkeydown = checkKey;
   function checkKey(e){
   e = e || window.event;
  
   if(e.keyCode=='40')
   {
     $('#autocomplete-results li:nth-child(0)').text('not working');
     console.log('here is 40'); //code
   }
  }
  </code></pre>
  
  <p>But it's not working - what do I need to change?</p>
  
  <p>thx in advance</p>