JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="dataR">

JavaScript

$(document).ready(function(){
    var semana = ["Domingo", "Segunda-Feira", "Terça-Feira", "Quarta-Feira", "Quinta-Feira", "Sexta-Feira", "Sábado"];
    $("input#dataR").blur(function(){
        var data = this.value;
        var arr = data.split("/").reverse();
        var teste = new Date(arr[0], arr[1] - 1, arr[2]);
        var dia = teste.getDay();
        alert(semana[dia]);
    });
});