JSFiddle - React, Tailwind, and code Playground

HTML

<!doctype html>
<html>
	<head>
		<meta charset="utf-8">
		<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
		<meta name="viewport" content="Width=device-Width, initial-scale=1">
		<link href="menu-vertical.css" rel="stylesheet" type="text/css" />
		<style>
			:root {
			--LeftSide: 50;
			}
			#menu-v li, #menu-v a {zoom:1;} /* Hacks for IE6, IE7 */
			#menu-v
			{
			width: 180px; /* Main Menu Item widths */
			border: 1px solid #ccc;
			border-top:none;
			position: relative; 
			font-size:0;
			list-style: none; 
			padding: 0; 
			display:block;
			margin-left: calc(var(--LeftSide) * 1px);
			margin-top: 40px!important;
			z-index:9;
			}
			#menu-v ul
			{
			width: 180px; /* Main Menu Item widths */
			border: 1px solid #ccc;
			border-top:none;
			position: relative; 
			font-size:0;
			list-style: none; 
			padding: 0; 
			display:block;
			margin: 0;
			z-index:9;
			}
			/* Top level menu links style
			---------------------------------------*/
			#menu-v li
			{
			background: #FFF url(bg.gif) repeat-x 0 2px;
			list-style: none; margin: 0; padding: 0;
			}
			#menu-v li a
			{
			font: normal 12px Arial;
			border-top: 1px solid #ccc;
			display: block;
			/*overflow: auto; force hasLayout in IE7 */
			color: black;
			text-decoration: none;
			line-height:26px;
			padding-left:26px;            
			}
			#menu-v ul li a
			{
			line-height:30px;
			}
			#menu-v li a.arrow:hover
			{
			background-image:url(arrowon.gif);
			background-repeat: no-repeat;
			background-position: 97% 50%;
			}
			/*Sub level menu items
			---------------------------------------*/
			#menu-v li ul
			{
			position: absolute;
			width: 200px; /*Sub Menu Items width */
			visibility:hidden;
			}
			#menu-v a.arrow
			{
			background-image:url(arrow.gif);
			background-repeat: no-repeat;
			background-position: 97% 50%;
			}
			#menu-v li:hover, #menu-v li.onhover
			{
			background-position:0 -62px;
			}
			#menu-v ul li
			{
			background: rgba(255, 255, 255,...