JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container common">
  <div class="child common">1</div>
</div>

CSS

div {
  margin: 10px;
}

JavaScript

$(document).ready(function(){
  let selector1 = '.common';
  let container = $('.container');
  container.find(selector1).addBack(selector1).css('border', '1px solid red');
  
  let selector2 = '.child';
  // container not selected
  container.find(selector2).addBack(selector2).css('background-color', 'lightblue');
})