JSFiddle - React, Tailwind, and code Playground

HTML

<button id="buttonAdd"type="button">ADICIONAR</button>
<a href="pagamentos.html">
<i class="fas fa-shopping-cart"></i>
<span class="badge badge-success" 
   id="carrinhoIndex">?</span></a>

JavaScript

var count = 0;
  var badge = $('#carrinhoIndex');
  badge.text(count);
  $(document).on('click', '#buttonAdd', function(e){
    e.preventDefault;
    count++;
    badge.text(count)
    });