jQuery last method

<!DOCTYPE html>
<html>
<head>
<title>jQuery Demo example</title>
 <script type="text/javascript" src="http://code.jquery.com/jquery-2.1.4.min.js">
 </script>
<script type="text/javascript">
         $(document).ready(function(){      
          $( "a" ).on( "click", function(event) {
                $("li").last().css("background","yellow");
             });          
          });
</script>
</head>	
<body>
<h4><a href="javascript:void(0);">Click Me to select last "li" element</a></h4>
<ul style="cursor:pointer;"> 
    <li>First Item (Index 0)</li>
    <li  class="second-li">Second Item ( Second li)
       <ul> 
          <li> Sub li 1</li>
          <li>Sub li 2</li>
          <li>Sub li 3</li>
          <li>Sub li 4</li>
      </ul>
    </li>
    <li>Third Item  (Index 2) </span></li>
     <li>Fourth Item  (Index 3)</li>
</ul>

</body>
</html>