JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr class="rowClass">
        <td>row 1</td>
    </tr>
    <tr class="rowClass">
        <td>row 2</td>
    </tr>
    <tr class="rowClass">
        <td>row 3</td>
    </tr>
</table>
<table>
    <tr class="rowClass">
        <td>row 1</td>
    </tr>
    <tr class="rowClass">
        <td>row 2</td>
    </tr>
    <tr class="rowClass">
        <td>row 3</td>
    </tr>
</table>

CSS

table {
    margin: 20px;
}
.eqd td {
    border: 1px solid orange;
}

JavaScript

$(function () {
    $('tr.rowClass:eq(1)').addClass('eqd');
    console.log($('tr.rowClass:eq(3)'));
});