JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <table class='forum-posts'>
        <tbody>
            <tr>
                <td>first row</td>
            </tr>
            <tr>
                <td>second row</td>
            </tr>
            <tr>
                <td>third row</td>
            </tr>
        </tbody>
    </table>
</body>

JavaScript

//var messages = document.getElementsByTagName('tr');
var messages = document.getElementsByClassName('forum-posts')[0].children[0].children;
var tablebody = document.createElement('tbody');
for (var i = messages.length - 1; i >= 0; i--) {
    var message = messages[i].outerHTML;
    tablebody.innerHTML = tablebody.innerHTML + message;
}

document.getElementsByClassName('forum-posts')[0].children[0].innerHTML = tablebody.innerHTML;