JSFiddle - React, Tailwind, and code Playground

HTML

<div id="main">
  <div id="footer"></div>
</div>

CSS

#main {
  height: 1000px;
  position: relative;
}

#footer {
  height: 64px;
  width: 100%;
  position: fixed;
  bottom: 0;
  background: #000;
  display: block;
}

JavaScript

window.addEventListener('scroll', function () {
	console.log('scroll: ' + (window.innerHeight + window.scrollY));
  console.log('height: ' + document.body.offsetHeight);
	if ((window.innerHeight + window.scrollY) >= document.body.offsetHeight) {
  	console.log('here!');
  }
});