JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li id="first">FirstLI
        <ul>
            <li>LI 1
                <ul style = "display:none">
                    <li> A</li>
            </ul>
               </li>
            <li>LI 2</li>
            <li>LI 3</li>
            <li>LI 4</li>
        </ul>
    </li>
</ul>

JavaScript

$('ul > li').hover(function(){
    $(this).children('ul').slideToggle();
}).children('ul').hide();