JSFiddle - React, Tailwind, and code Playground

HTML

<div class="menuD">Menu</div>

CSS

body {
  height: 800px;
}

.menuD {
  position: absolute;
  top: 190px;
}

.bottom {
  top: 590px;
}

JavaScript

let menu = document.querySelector('.menuD');

window.onscroll = function(ev) {
    if ((window.innerHeight + window.scrollY) >= document.body.offsetHeight) {
        menu.classList.add('bottom');
    } else {
    	 menu.classList.remove('bottom');
    }
};