JSFiddle - React, Tailwind, and code Playground

HTML

<div id="parent">
 <div class="child first">
   <div class="sub-child">1</div>
 </div>

 <div class="child second">
   <div class="sub-child">2</div>
 </div>

 <div class="child third">
   <div class="sub-child">3</div>
 </div>
</div>

JavaScript

var $children = $('#parent .child').click(function () {
    console.log($children.index(this));
});