JSFiddle - React, Tailwind, and code Playground

HTML

<pre id="repeat"></pre>

<div style="position:relative;">
    <div id="show">x</div>
</div>

CSS

#show {
    display:block;
    position:fixed;
    top:0px;
    left:300px;
}

JavaScript

var elem = document.getElementById('repeat');
var show = document.getElementById('show');

for (i = 1; i <= 300; i++) {
    elem.innerHTML += i + "<br/>";
}


window.onscroll = function () {
    show.innerHTML = document.body.scrollTop;
};