JSFiddle - React, Tailwind, and code Playground

HTML

<canvas></canvas>
<button type="button" id="b1">Heloł</button>

CSS

canvas{width:200px; height:200px; background:#000;}
button{background:#ccc; color:#000; border:none; padding:10px;
    position:absolute; top:100px; left:100px; z-index:5;
}

JavaScript

document.getElementById("b1").addEventListener("click", function(){
    alert('O, jak klikłem!');
});