JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li>Parent</li>
    <li>Parent2</li>
    <li>Parent3
      <ul>
          <li>child</li>
      </ul>              
    </li>
</ul>

CSS

ul li ul {
    display: none
}

JavaScript

$('ul').mouseout(function() {
        $(this).children('li ul').each(function () {
            $(this).slideUp('slow');
        });
    });

    $("ul li").hover(function() { $(this).children('ul').slideDown('slow'); });