JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="level-1">
  <li class="item-i">I</li>
  <li class="item-ii">II
    <ul class="level-2">
      <li class="item-a">A</li>
      <li class="item-b">B
        <ul class="level-3">
          <li class="item-1">1</li>
          <li class="item-2">2</li>
          <li class="item-3">3</li>
        </ul>
      </li>
      <li class="item-c">C</li>
    </ul>
  </li>
  <li class="item-iii">III</li>
</ul>

JavaScript

$(function() {
     $('li.item-ii').find('li').css('background-color', '#ABABAB'); 
     $('ul, li').filter('[class$=3]').css('border', 'black 2px solid');
});