JSFiddle - React, Tailwind, and code Playground

HTML

<div id="next">Test</div>
<div id="value"></div>

CSS

#next {
    width:100%;
    height:100%;
    background-color:red;
    display:none;
}

JavaScript

function show() {
    document.getElementById('next').style.opacity = (parseFloat(document.getElementById('next').style.opacity) + 0.1);
    document.getElementById('value').innerHTML = (document.getElementById('next').style.opacity);
    if (document.getElementById('next').style.opacity < 1) {
        setTimeout(show, 400);
    }
}

function fadeIn() {

    document.getElementById('next').style.opacity = 0;
    document.getElementById('next').style.display = 'block';
    setTimeout(show, 400);
}

fadeIn();