JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://malihu.github.io/custom-scrollbar/3.0.0/jquery.mCustomScrollbar.concat.min.js"></script>
<link rel="stylesheet" href="http://malihu.github.io/custom-scrollbar/3.0.0/jquery.mCustomScrollbar.min.css">
<button id="button">Click</button>
<div id="wrapper">
    <div id="left-menu-top">
		<p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Ut tristique laoreet dui, id porttitor ipsum convallis vel. Integer turpis nisl, rhoncus sed hendrerit sit amet, adipiscing nec eros. Suspendisse potenti. Nam quis risus libero. Vestibulum et diam nisl, eget feugiat leo. Quisque rutrum fermentum leo, sit amet semper eros elementum eu. Donec aliquam magna et sem condimentum rutrum. Sed augue nulla, rhoncus venenatis scelerisque sed, accumsan sed magna. In hac habitasse platea dictumst. Ut quis felis dui. Vestibulum ante ipsum primis in faucibus orci luctus et ultrices posuere cubilia Curae; Praesent ornare enim pharetra justo gravida sed fringilla ipsum porttitor. Nunc vitae erat vitae magna rhoncus sagittis vel non nunc. Curabitur et lectus eu elit sollicitudin lacinia ac id nisi. Morbi mi augue, elementum id laoreet ut, dignissim vel neque. Aliquam erat volutpat.</p>
    			
	</div>
</div>

CSS

* {
  box-sizing: border-box;
}

html {
	height:100%;
	overflow-y:hidden;
}

body {
	height:100%;
	position:relative;
	margin:0;
	padding:0;
}

p {margin:0;}

#wrapper {	
 /* padding:8px;*/
  top:8px;
  left:8px;
  width:340px;
  height: auto;
  max-height:calc(100% - 38px);
  position:fixed;
  overflow: auto;

  
}

#left-menu-top {
    width: auto;
	display:block;
	  background-color: #000000;
  background-color: rgba(0, 0, 0, 0.8);
}

#button {
	bottom:10px;
	position:absolute;
}

JavaScript

(function($){
        $(window).load(function(){
            $("#wrapper").mCustomScrollbar({
					scrollButtons:{
						theme:"light"
					}
				});
        });
    })(jQuery);