JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td>a</td>
        <td>b</td>
        <td>c</td>
        <td>d</td>
        <td style="display:none;">1</td>
    </tr>
</table>

CSS

table {
    margin: 25px;
}
tr {
    background-color: #c00;
    color: #fff;
    border: 1px solid #000;
    padding: 10px;
}

JavaScript

$("tr").click(function()
{
    var row = $(this);
    var visibleLength = row.find("td:visible").length;
    var hiddenLength = row.find("td:not(:visible)").length;
    var drillRow = $("<tr/>").addClass("drillDownRow");
    var drillColumn = $("<td/>").attr("colspan", visibleLength);
    var drillHidden = $("<td/>").attr("colspan", hiddenLength).css({display: "none"});
    
    drillColumn.html("test <b>2</b>... ok");
    
    drillRow.hide().append(drillColumn).append(drillHidden).insertAfter(row);
    drillRow.slideDown("slow",function() {$(this).css({display: "table-row"})});
});