JSFiddle - React, Tailwind, and code Playground

HTML

Este input ignora vogais!
<input type="text" />

JavaScript

var input = document.querySelector('input');
var ignorar = ['a', 'e', 'i', 'o', 'u'];
input.addEventListener('keydown', function (e) {
    var char = e.keyCode || e.which;
    var letra = String.fromCharCode(char).toLowerCase();
    if (ignorar.indexOf(letra) != -1) e.preventDefault();
});