JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li>
    <a href="parent.html">Parent</a>
    <ul class="children">
      <li>
        Ololololo Hide
        <li>
    </ul>
    </li>
    <li class="current_page_parent">
      <a href="parent.html">Parent</a>
      <ul class="children">
        <li>
          Ololololo Show
          <li>
      </ul>
      </li>
      <li class="current_page_parent2">
        <a href="parent.html">Parent</a>
        <ul class="children">
          <li>
            Ololololo Hide
            <li>
        </ul>
        </li>
</ul>
<ul class="children">
  <li>
    Ololololo Hide
    <li>
</ul>

JavaScript

$(".children").not(".current_page_parent .children").hide();