JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td rowspan="2">First</td>
        <td> First 1 1 </td>
        <td> First 2 1 </td>
    </tr>
    <tr>
         <td> First 2 1 </td>
         <td> First 2 2 </td>
    </tr>
    <tr>
        <td rowspan="2">Second</td>
        <td> Second 1 1 </td>
        <td> Second 2 1 </td>
    </tr>
    <tr>
         <td> Second 2 1 </td>
         <td> Second 2 2 </td>
    </tr>
</table>

JavaScript

var table = $('table');
$('td').click(function() {
  var perent = $(this).parent();
      index= table.find(perent).index();
   alert( index );
})