JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>

CSS

div{
   width:200px; 
   height:100px;
   background-color:red;
}
div.modal-width{
   width:100px; 
   background-color:blue;
}

JavaScript

function checkHeight() {
  if ($(window).height() < 800) 
      $('div').addClass('modal-width');
  else
      $('div').removeClass('modal-width');
}

$(window).resize(checkHeight);