JSFiddle - React, Tailwind, and code Playground

CSS

.popup {
    background:#fff;
    border-radius:3px;
    padding:10px;
    box-shadow:0 0 0 rgba(0, 0, 0, 0.2), 0 0 0 1000px rgba(0, 0, 0, 0.4);
    position:absolute;
    top:50%;
    left:50%;
    -webkit-transform:translateX(-50%) translateY(-50%);
}

JavaScript

var popup = (function () {
    return {
        confirm: function () {
            $('body').append('<div class="popup"><button>Confirmar?</button></div>');
            // ?
        }
    };
})();

//testando
if (popup.confirm()) {
    alert('Confirmado!');
}