JSFiddle - React, Tailwind, and code Playground

HTML

<table id="map">
    <tr>
        <td>1</td>
        <td>2</td>
        <td>3</td>
    </tr>
</table>

JavaScript

$(document).ready(function(){
        $('#map').on('mouseenter', 'td:last-child', function(){
            var tdId = $(this).attr('id');
            var newId = parseInt(tdId);
            $(this).after('<td>new</td>');
        });         
    });