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>

CSS

body {
    font-family: Verdana, Arial, sans-serif;
    font-size: 12px;
}

JavaScript

$(document).ready(function() {
    $("td").click(function() {
        var $this = $(this);
        var rowIndex = $this.closest("tr").index();
        $this.closest("table").find("tr").map(function() {
            return $(this).find("td:first").attr("rowspan") || 1;
        }).each(function(index) {
            if ((rowIndex -= this) < 0) {
                alert(index + 1);
                return false;
            }
        });
    });
});