JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="nav">
<li class="parent over"><a href="/category/santehnika"><span>Сантехника</span></a>
<ul>
<li style="display: list-item; "><a href="/category/fajns"><span>фаянс</span></a></li>
<li class="parent" style="display: list-item; "><a href="/category/mixers"><span>Смесители</span></a>
<ul>
<li style="display: none; "><a href="/category/sink"><span>для раковины</span></a></li>
<li style="display: none; "><a href="/category/bathroom"><span>для ванной</span></a></li>
<li style="display: none; "><a href="/category/shower"><span>для душа</span></a></li>
<li style="display: none; "><a href="/category/kitchen"><span>для кухни</span></a></li>
<li class="last" style="display: none; "><a href="/category/bidet"><span>для биде</span></a></li>
</ul>
</li>
<li class="parent last" style="display: list-item; "><a href="/category/bathaccessories"><span>Аксессуары для ванной</span></a>
<ul>
<li style="display: none; "><a href="/category/holders"><span>держатели</span></a></li>
<li style="display: none; "><a href="/category/hooks"><span>крючки</span></a></li>
<li style="display: none; "><a href="/category/shelves"><span>полки</span></a></li>
<li style="display: none; "><a href="/category/glasses"><span>стаканы</span></a></li>
<li class="last" style="display: none; "><a href="/category/soapdishes"><span>мыльницы</span></a></li>
</ul>
</li>
</ul>
</li>
</ul>

JavaScript

$(document).ready(function() {
    $('ul#nav li.parent > a').click(
        function(){                                               $(this).parent().find('li').slideToggle('middle');
      return false;
                   });

$('ul#nav li.parent ').find('li').slideToggle('fast');
                                });