问jquery外部选择器标记(class或id)

EN

<td>
   <input type="text" name="c_name[]" class="form-control cast-name" id="cast1" autocomplete="off">
   <div class="cast-search">
       <div class="cast-pop">
          <ul>  
            <li class="item">1</li>
            <li class="item">2</li>
            <li class="item">3</li>
          </ul>
       </div>
   </div>
</td>
<td>
   <input type="text" name="c_name[]" class="form-control cast-name" id="cast2" autocomplete="off">
   <div class="cast-search">
       <div class="cast-pop">
          <ul>  
            <li class="item">1</li>
            <li class="item">2</li>
            <li class="item">3</li>
          </ul>
       </div>
   </div>
</td>

$('body').on('keyup','.cast-name',function(){
        $(this).next().slideDown(200);
        var datas = $(this).val();
        var cast_pop = document.getElementsByClassName('cast-pop');
        $.ajax({
            url:"include/film/cast_get.php",
            type:"GET",
            data:'cast='+datas,
            success:function(answer){
                $('.cast-pop').html(answer);
                $('.item').click(function(){
                    // how will I do ... 
               }
            }
        });
    });