JSFiddle - React, Tailwind, and code Playground

HTML

<div id="trans"></div>
<input type="button" onclick="add(document.getElementById('trans'), 0.1)" value="add Opacity">

CSS

#trans
{
    height: 100px;
    width: 100px;
    background-color: green;
}

JavaScript

trans = document.getElementById("trans");
trans.style.opacity = 1;

var add = function(ele, amount)
{
    if(ele.style.opacity >= amount)
        ele.style.opacity -= amount;
};