JSFiddle - React, Tailwind, and code Playground

HTML

<button id="btnAdd" name="btnAdd" class="span1" >ADD</button>
<table class="td1" style="display: block;" >
<tr id="td1" >  
     <td><input type="text" name="val1" id="val1"/></td>
     <td><input type="text" name="val2" id="val2"/></td>
</tr>
</table>

JavaScript

$('#btnAdd').on('click', function (e) {
        e.preventDefault();
        var elem = $(this).next('.td1')
        elem.toggle('slow');
    });