JSFiddle - React, Tailwind, and code Playground

HTML

<div id="owner">
  <div class="parent one">                <!-- parent lvl 1 -->
    <div class="child one">               <!-- child lvl 1 -->
      <div class="parent two">            <!-- parent lvl 2 -->
        <div class="child two"></div>     <!-- child lvl 2 -->
        <div class="child two"></div>
        <div class="child two"></div>
      </div>
    </div>
    <div class="child one"></div> 
    <div class="child one"></div> 
    <div class="child one"></div> 
  </div>
</div>

JavaScript

var el = document.getElementById("owner");
console.info(el && el.querySelectorAll('.parent .child'));