JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>

CSS

body::before {
  content: "I'm not mobile!";
}
body.mobile::before {
  content: "I'm mobile!";
}

JavaScript

$(document).on('click', 'body.mobile .mobileNavButton', function() {
    $('.mainNav').toggleClass('active');
    $('.mobileNavButton').toggleClass('active');
});

$(document).on('click', 'body.mobile .hasDropdown', function() {
   $('.dropdown').toggle('slide');
    $('.dropdown').toggleClass('active');
    $('.hasDropdown').toggleClass('rotate');
});

$(document).on('click', 'body.mobile .hasSubDropdown', function() {
    $('.subDropdown').toggle('slide');
    $('.subDropdown').toggleClass('active');
    $('.hasSubDropdown').toggleClass('rotate');
});

$(window).resize(function(e) {
    if ($(window).width() <= 800) {
        $('body').addClass('mobile');
    }
    else {
        $('body').removeClass('mobile');
    }
});

$(document).ready(function(){
  $(window).resize(); // call once for good measure!
});