JSFiddle - React, Tailwind, and code Playground

HTML

<p>I am text.</>

CSS

html {
    background: white;
    color: red;
    font-size: 1.4em;
}
html.mobile {
    background: blue;
    color: white;
    font-size: 1em;
}

JavaScript

$(window).on('resize', function(){
      var win = $(this);
      if (win.width() < 514) { 

      $('html').addClass('mobile');

      }
    else
    {
        $('html').removeClass('mobile');
    }

});