JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <thead>
        <tr>
            <th>Header 1</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <td>Content 1</td>
        </tr>
    </tbody>
</table>

CSS

tbody tr {
    color: red;
}

JavaScript

var t = "<tr><th>Header 2</th></tr>";
$('table').find('thead').append(t);