JSFiddle - React, Tailwind, and code Playground

HTML

Digite por exemplo a letra "M" pequena e grande:
<input type="text" />
<div id="res"></div>

JavaScript

var input = document.querySelector('input');

function log(e) {
    var char = e.code || e.keyCode || e.which;
    var res = [e.type, char, String.fromCharCode(char), '<br />'].join(' | ');
    document.getElementById('res').innerHTML += res;
};

input.addEventListener('keydown', log);
input.addEventListener('keypress', log);
input.addEventListener('keyup', log);