JSFiddle - React, Tailwind, and code Playground

HTML

<div id="loader">
loading...
</div>

CSS

#loader {
  background: #ff0;
  text-align: center;
  padding: 50px;
  display: none;
}

JavaScript

$(document).ready(function() {
	window.addEventListener('beforeunload', showLoader);
});

var showLoader = function() {
	$('#loader').show();
};