<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css"> <script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <!------ Include the above in your HEAD tag ----------> <div class="container"> <div class="row"> <h2>Create your snippet's HTML, CSS and Javascript in the editor tabs</h2> <pre class="line-numbers"> <code class="language-js"> init: function() { var scroll_theme=($('.main-menu').hasClass('menu-dark')) ? 'light': 'dark'; this.obj=$(".main-menu-content").perfectScrollbar( { suppressScrollX: true, theme: scroll_theme } ); } , update: function() { if (this.obj) { $(".main-menu-content").perfectScrollbar('update'); } } , enable: function() { this.init(); } </code> </pre> </div> </div>