JSFiddle - React, Tailwind, and code Playground

by defmetalhead

HTML

<ul class="mainList">
  <li>1</li>
  <li>2</li>
  <li>3
    <ul>
    <li style="display: none;">3-1</li>
    <li style="display: none;">3-2</li>
    <li style="display: none;">3-3</li>
    <li style="display: none;">3-4</li>
      </ul></li>
  <li>4</li>
  <li>5</li>
  <li>6</li>
  <li>7</li>
  <li>8</li>
</ul>

CSS

.clear{background:#F00}

JavaScript

$('.mainList').children('li:nth-child(3n+4)').addClass('clear');