问单击事件时显示文本框长度

EN

   <div class="title" style="padding:20px 0 ">
   <input type="text" class="form-control txtKeywords" maxlength="80" placeholder="Click on keywords to combine your title">
   <span id="displayChar"></span>
   </div>

  $('#displayChar').text("Title contains: 0/80 characthers");

 $('.txtKeywords').on('keyup',function(){
            var input = $(this);
            input.next("span").text("Title contains: "+ input.val().length + "/80 characthers");
        });

 <tr>
 <td class="keywordClick" value="@item.Keyword"><h5 style="cursor:pointer;">@item.Keyword</h5></td>
<td><b>@item.Sales</b></td>
</tr>

  $(document).on("click", ".keywordClick", function () {
            var appendText = " " + $(this).attr('value');
            if ($('.txtKeywords').val().length < 80) {
               // somehow here modify  the span value to display .txtKeywords current length 
                $('.txtKeywords').val(function (index, val) {
                    return val+appendText;
                });
            }
            else {
                ShowErrorMessage("Title can have maximum of 80 characters.")
            }
        });