JSFiddle - React, Tailwind, and code Playground

HTML

<button>Click Here</button>
<table>
    <tr>
        <td class="top">TOP</td>
    </tr>
    <tr>
        <td>A</td>
        <td>B</td>
        <td>C</td>
        <td>D</td>
        <td>E</td>
        <td>F</td>
    </tr>
</table>

CSS

table
{
    border:1px solid black;
}
td
{
    border:1px solid black;
}

JavaScript

$('button').click(function() {
    if ($('.top').attr('colspan')) {
        $('.top').removeAttr('colspan');
    } else {
        $('.top').attr('colspan', 6);
    }
});