JSFiddle - React, Tailwind, and code Playground

HTML

<h2 id='pressed'>Teclas pressionadas: </h2>

JavaScript

var pressed = document.getElementById('pressed');

function keyPressed(evt){
    evt = evt || window.event;
    var key = evt.keyCode || evt.which;
    return String.fromCharCode(key); 
}

document.onkeypress = function(evt) {
    var str = keyPressed(evt);
    pressed.innerHTML += str;
};