I want to add (data-row-num=”1″,data-row-num=”2″,data-row-num=”3″) for my HTML table row.
Can someone please help me to do it like ?

<table id="example" class="table table-striped first-table" style="width:100%">
    <thead>
        <tr>
            <th>Name</th>
            <th>Position</th>
            <th>Office</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>Tiger Nixon</td>
            <td>System Architect</td>
            <td>Edinburgh</td>
        </tr>
           <tr>
            <td>Cedric Kelly</td>
            <td>Senior Javascript Developer</td>
            <td>Edinburgh</td>
        </tr>
        
      </tbody></table>
<script type="text/javascript">
$(document).ready(function() {
        $('#example').dataTable( {  } );
} );

  $("tr").each(function() {
      $("tr").attr("data-row-num",????); 
}); 
<script>