JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text"><br>
    IVA calculado al 15%: <span></span><br>
    Valor total: <p></p><br>

JavaScript

$(document).ready(function(){
    $('input').keyup(function(){
        num = parseFloat($(this).val());
        IVA = num * 0.15;
        total = num + IVA;
        $('span').html(IVA);
        $('p').html(total);
    });
});