JSFiddle - React, Tailwind, and code Playground

HTML

<table id="table" border="1">
    <tr id="header">
        <td colspan="2">
            header goes here
        </td>
    </tr>
    <tr>
        <td>
            the second
        </td>
        <td>
            row
        </td>
    </tr>
</table>

JavaScript

$(document).ready(function() {
    $("#table tr:first").after("<tr><td>some</td><td>content</tr></tr>");
});