JSFiddle - React, Tailwind, and code Playground

HTML

<div id="container">
    <div id="scroller"></div>
</div>

CSS

#container {
    height: 5000px;
    width: 100%;
}
#scroller {
    height: 25px;
    width: 25px;
    background-color: black;
    position: fixed;
}

JavaScript

window.addEventListener("scroll", myFunc.bind(this, document.getElementById("scroller")), false);

function myFunc(div) {
    var scroll = document.body.scrollTop;
    div.style.top = (scroll / 10)+"px";
};