JSFiddle - React, Tailwind, and code Playground

HTML

<table>
  <tr>
    <td>iten</td>
    <td>preco</td>
    <td>qtd</td>
  </tr>
  <tr>
    <td>Teste</td>
    <td>R$99,99</td>
    <td class="addqt">1</td>
  </tr>
  <tr>
    <td>Teste2</td>
    <td>R$66,99</td>
    <td class="addqt">4</td>
  </tr>
  <tr>
    <td>Teste3</td>
    <td>R$11,99</td>
    <td class="addqt">6</td>
  </tr>
</table>

<div class="thumbnail">
<button id="add" type="button">+</button>
</div>

JavaScript

$('#add').on('click', function (e) {

  e.preventDefault();

 $('.addqt').each(function(index){
 	var qt = $(this).text()
  $(this).text(++qt);
 });

});