JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.4.min.js"></script>
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.14.0/css/all.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/5.14.0/js/all.min.js"></script>
<a href="javascript:void(0);" onclick="toggleNav()">
<span class="ico"><i class="fa fa-bars hvr-icon"></i></span> Dashboard
</a>

<ul id="submenu">
<li>Example Menu</li>
<li>Example Menu 2</li>
<li>Example Menu 3</li>
</ul>

CSS

#submenu {
  display:none;
}

JavaScript

function toggleNav() {
    $("#submenu").toggle();
}