JSFiddle - React, Tailwind, and code Playground
by CSS_Apprentice
HTML
<ul class="main-section-nav nav navbar-nav">
<li class="dropdown">
<a>item</a>
<ul>
<li> item </li>
<li> item </li>
<li> item </li>
</ul>
</li>
<li class="dropdown active">
<a>item</a>
<ul>
<li> item </li>
<li> item </li>
<li> item </li>
</ul>
</li>
<li class="dropdown">
<a>item</a>
<ul>
<li> item </li>
<li> item </li>
<li> item </li>
</ul>
</li>
<li class="dropdown">
<a>item</a>
<ul>
<li> item </li>
<li> item </li>
<li> item </li>
</ul>
</li>
</ul>
CSS
.dropdown > ul {display: none}
.dropdown.open > ul {display: block}
JavaScript
$('.main-section-nav > li').mouseleave(function(){
$('.active').addClass('open');
});