JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tabs">
  <ul>
    <li><a href="#tabs-1">Tab 1</a></li>
    <li><a href="#tabs-2">Tab 2</a></li>
  </ul>
  <div id="tabs-1">
    <div class="subtabs">
      <ul>
        <li><a href="#tabs-1a">Tab 1-A</a></li>
        <li><a href="#tabs-1b">Tab 1-B</a></li>
      </ul>
      <div id="tabs-1a">
        <p>Tab 1A</p>
      </div>
      <div id="tabs-1b">
        <p>Tab 1B</p>
      </div>
    </div>
  </div>
  <div id="tabs-2">
    <div class="subtabs">
      <ul>
        <li><a href="#tabs-2a">Tab 2-A</a></li>
        <li><a href="#tabs-2b">Tab 2-B</a></li>
      </ul>
      <div id="tabs-2a">
        <p>Tab 2A</p>
      </div>
      <div id="tabs-2b">
        <p>Tab 2B</p>
      </div>
    </div>
  </div>
</div>

JavaScript

$('.tabs').tabs();
    $('.subtabs').tabs({
        activate: function( event, ui ) {
            //get relative li index
            var secondTabSelected = $(ui.newTab).index();
            console.log(secondTabSelected);
        }
    });