title: apply css to another span on slide of a carousel
body: <p>I have a carousel running at my site </p>
  
  <pre><code>div id="weekCarousel_{{$index}}" class="carousel slide"&gt;
      &lt;a href="#weekCarousel_{{$index}}" data-slide="prev" class="prevweek"&gt;
          &lt;span class="glyphicon glyphicon-chevron-left" aria-hidden="true"&gt;&lt;/span&gt;
      &lt;/a&gt;
      &lt;a href="#weekCarousel_{{$index}}" data-slide="next" class="nextweek"&gt;
          &lt;div class="glyphicon glyphicon-chevron-right" aria-hidden="true"&gt;&lt;/div&gt;
      &lt;/a&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I would like to add a css class for span whenever this carousel gets slided </p>
  
  <pre><code>&lt;span id="displayer"&gt;.........&lt;/span&gt;
  </code></pre>
  
  <p>this is my span tag any suggestions?</p>