JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="menu">
    <div class="drop">
        <li ><a href="#">Home</a></li>
        <li class="menu-item-has-children highlight"><a href="#" class="">HOVER ME!!</a>    
            <div class="drop">
                <ul class="sub-menu">
                    <li class="menu-item-has-children highlight"><a href="#" class="">2nd Level Page</a>
                        <div class="drop">
                            <ul class="sub-menu">		
                                <li class="highlight"><a href="#">3rd Level Page</a></li>
                                <li class="highlight"><a href="#">Another 3rd Level Page</a></li>
                            </ul>
                        </div>
                    </li>
                </ul>
            </div>
        </li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
        <li class="highlight"><a href="#">Link</a></li>
    </div>
</ul>
<div class="content">
<p>orem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of...

CSS

html,body { height:100%; margin:0;}
p {margin:0;}
.menu	{
	    padding: 0;
	    margin: 0;
	    position: absolute;
	    z-index: 9998;
	    top:0;
	    left:0;
	    background: white;
	    width: 280px;
			-webkit-backface-visibility: hidden;
		  backface-visibility: hidden;
			    height:100%;
	}

	.menu li.highlight {
	    -webkit-transition: all .1s cubic-bezier(.77,0,.175,1) .1s;
	    -moz-transition: all .1s cubic-bezier(.77,0,.175,1) .1s;
	    -ms-transition: all .1s cubic-bezier(.77,0,.175,1) .1s;
	    transition: all .1s cubic-bezier(.77,0,.175,1) .1s;
			-webkit-backface-visibility: hidden;
		  backface-visibility: hidden;
	}

	.menu li.highlight:hover {
	    -webkit-transition: all .3s cubic-bezier(.77,0,.175,1) .7s;
	    -moz-transition: all .3s cubic-bezier(.77,0,.175,1) .7s;
	    -ms-transition: all .3s cubic-bezier(.77,0,.175,1) .7s;
	    transition: all .3s cubic-bezier(.77,0,.175,1) .7s;
        background: pink;
			-webkit-backface-visibility: hidden;
		  backface-visibility: hidden;
	}

	.menu li > .drop li > .drop li.current-menu-item a,
	.menu li > .drop li.current-menu-item a,
	.contact.open a { color: #fff ; }

	.menu li {
	    height: auto;
	    width: 100%;
	    list-style: none;
		 border-bottom: 2px solid #f0f0f0;
		 -webkit-backface-visibility: hidden;
 	  backface-visibility: hidden;
		background: #fff;
		-webkit-user-select: none;
-webkit-touch-callout: none;
	}

	.menu li a {
	    color: #aaa;
	    text-transform: uppercase;
	    font-size:12px;
	    padding: 0 35px;
	    display: inline-block;
	    width: 100%;
		 line-height: 1.4em;
		 height:58px;
		 -moz-box-sizing: border-box;
			-webkit-box-sizing: border-box;
			box-sizing: border-box;
	}

		/* Sweep To Right */
		.menu li a {
		  display: inline-block;
		  vertical-align: middle;
		  -webkit-transform: translateZ(0);
		  transform: translateZ(0);
		  box-shadow: 0 0 1px rgba(0, 0, 0, 0);
		  -webkit-backface-visibility: hidden;
		  backface-visibility: hidden;
		 ...

JavaScript

var menuHeight = $('.content').outerHeight(true );
$('.menu').css({
    'height': menuHeight + 'px'
});