JSFiddle - React, Tailwind, and code Playground

HTML

<div data-name="alex"></div>

CSS

div {
    background-color: black;
    width: 50px;
    height: 50px;
}

JavaScript

var elem = document.querySelector('div[data-name="alex"]');
elem.onmouseover = function() {
    this.style.opacity = '0';
}
elem.onmouseleave = function() {
    this.style.opacity = '1';
}