如何显示最后一个重复值的错误消息

Question

我想使用jquery.table值在表中显示最后一个重复值的错误消息，我正在添加dynamicaly.So怎么办？请分享您的想法以解决此问题。

$(document).ready(function() {
  $("#btnSave").click(function() {
    var arr = [];
    var tblid = $("#comp tr");
    tblid.each(function() {
      arr.push($(this).find('td').find('span').attr('data-id'));
    });
    alert(arr);
  });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<table id="comp">
  <tr>
    <td><span data-id="kiste"></span>kiste
      <p class="close">
        Same Name so please change
      </p>
    </td>
  </tr>
  <tr>
    <td><span data-id="Futiste"></span>Futiste
      <p class="close">
        Same Name so please change
      </p>
    </td>
  </tr>
  <tr>
    <td><span data-id="kavi"></span>kavi
      <p class="close">
        Same Name so please change
      </p>
    </td>
  </tr>
  <tr>
    <td><span data-id="kiste"></span>kiste
      <p class="close">
        Same Name so please change
      </p>
    </td>
  </tr>
  <tr>
    <td><span data-id="Futter"></span>Futter
      <p class="close">
        Same Name so please change
      </p>
    </td>
  </tr>
</table>

<button id="btnSave">Save Click</button>