JSFiddle - React, Tailwind, and code Playground

HTML

<table id="myID" class="myClass">
    <tr>
        <th>one</th>
        <th>two</th>
        <th>three</th>
        <th>four</th>
    </tr>
        <tr>
        <td>1</td>
        <td>2</td>
        <td>3</td>
        <td>4</td>
    </tr>
    <tr>
        <td>a</td>
        <td>b</td>
        <td>c</td>
        <td type='checkbox'></td>    <!--  **THIS IS WAHT IM AFTER**  -->
    </tr> 
   </table>

JavaScript

$('#myID tr').find("td").last().append("<input type='checkbox' />");