JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tbody>
        <tr>
            <td> Item 1 </td>
            <td> Item 2 </td>
        </tr>
        <tr>
            <td> Item 1 </td>
            <td> Item 2 </td>
        </tr>
        <tr>
            <td> Item 1 </td>
            <td> Item 2 </td>
        </tr>
    </tbody>
</table>

<button id='adder'>Add Row</button>

CSS

.alt {
    background: #CCC;   
}

JavaScript

$(document).ready(function() {
    $('tr').filter(':odd').addClass('alt');

    $('#adder').click(function() {
        $('tbody').append('<tr><td>Item 1</td><td>Item 2</td></tr>');
        $('tr').filter(':odd').addClass('alt');
    });
});