title: how to find active class data-id
body: <pre><code>&lt;ul class="deal-menu"&gt;
     &lt;li class="active" data-id="today-spl"&gt;&lt;a href="#" class="first"&gt;Special&lt;span class="active"&gt;&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
     &lt;li class="" data-id="today-deal"&gt;&lt;a href="#"&gt;Deal&lt;/a&gt;&lt;span&gt;&lt;/span&gt;&lt;/li&gt;
     &lt;li class="" data-id="today-spl"&gt;&lt;a href="#" class="last"&gt;TDeal&lt;span&gt;&lt;/span&gt;&lt;/a&gt;&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>my jquery code is </p>
  
  <pre><code>function addcls() {
          var current = $('.deal-menu li.active').removeClass('active'),
              next = current.next().length ? current.next() : current.siblings().filter(':first');
          next.addClass('active');
          var val = $(this).data("id");
          alert(val);
      };
  
   setInterval(function () {
          addcls();
         }, 3000);
  </code></pre>
  
  <p>i need to find the active class data-id value , its showing undefined value</p>