JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text">
<input type="text">
<input type="text">
<textarea name="" id="" cols="30" rows="5"></textarea>
<br>
<button disabled>Enviar!</button>

CSS

input, textarea, select {
    display:block;
}

JavaScript

function isAnyEmpty(el) {
    var isEmpty = false,
        v;
    el.each(function (e) {
        v = $(this).val();
        if (v == "" || v == null || v == undefined) {
            isEmpty = true
        }
    });
    return isEmpty;
}

var el = $('input, textarea, select');

el.on('keyup', function () {
    console.log(isAnyEmpty(el));
    $('button').prop('disabled', isAnyEmpty(el));
});