JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<div class="row div-categoria">
  <div class="row">
    <div class="col-lg-2 col-md-4 col-sm-6">
      <button type="button" class="btn btn-primary btn-salvar">
        Salvar
      </button>
    </div>
  </div>
  <div class="row">
    <div class="col-lg-12 col-md-12 col-sm-12">
      <table class="table" data-idx="1">
        <thead>
          <tr>
            <th>Firstname</th>
            <th>Lastname</th>
            <th>Email</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td>John</td>
            <td>Doe</td>
            <td>[email protected]</td>
          </tr>
          <tr>
            <td>Mary</td>
            <td>Moe</td>
            <td>[email protected]</td>
          </tr>
          <tr>
            <td>July</td>
            <td>Dooley</td>
            <td>[email protected]</td>
          </tr>
        </tbody>
      </table>
    </div>
    </div>
</div>
<div class="row div-categoria">
  <div class="row">
    <div class="col-lg-2 col-md-4 col-sm-6">
      <button type="button" class="btn btn-primary btn-salvar">
        Salvar
      </button>
    </div>
  </div>
  <div class="row">
    <div class="col-lg-12 col-md-12 col-sm-12">
      <table class="table"  data-idx="2">
        <thead>
          <tr>
            <th>Firstname</th>
            <th>Lastname</th>
            <th>Email</th>
          </tr>
        </thead>
        <tbody>
          <tr>
            <td>John</td>
            <td>Doe</td>
            <td>[email protected]</td>
          </tr>
          <tr>
            <td>Mary</td>
            <td>Moe</td>
            <td>[email protected]</td>
          </tr>
          <tr>
            <td>July</td>
            <td>Dooley</td>
            <td>[email protected]</td>
          </tr>
        </tbody>
      </table>
    </div>
    </div>
</div>
<div class="row div-categoria">
  <div class="row">
    <div class="col-lg-2 col-md-4 col-sm-6">
     ...

JavaScript

$(".btn-salvar").click(function(){
	var table = $(this).closest(".div-categoria").find("table");
	alert($(table).attr("data-idx"));
});