JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td>A</td>
        <td>B</td>
        <td>C</td>
        <td>D</td>
        <td>E</td>
        <td>F</td>
        <td>G</td>
        <td>H</td>
        <td>I</td>
        <td>J</td>
        <td>K</td>
        <td>L</td>
        <td>M</td>
        <td>N</td>
        <td>O</td>
    </tr>
</table>
<hr>
<table>
<tr>
<td>
A
</td>
<td>
B
</td>
</tr>
<tr>
<td>
C
</td>
<td>
D
</td>
</tr>
</table>

JavaScript

var cols = 1;
$('tr').each(function () {
    var after = $(this);
    while ($(this).children().length > cols) {
        after = $('<tr>').insertAfter(after).append($('>:gt(' + (cols - 1) + '):lt(' + (cols) + ')', this));
    }
})