Positive date period validation gives Nan error

Question

I got it on my JS

var inicioFerias = new Date($("#txtInitialVacancies").val());
var fimFerias = new Date($("#txtFinalVacancies").val());

var utc1 = Date.UTC(fimFerias.getFullYear(), fimFerias.getMonth(), fimFerias.getDate());
var utc2 = Date.UTC(inicioFerias.getFullYear(), inicioFerias.getMonth(), inicioFerias.getDate());

        var diffDays = Math.ceil((utc1 - utc2) / (1000 * 60 * 60 * 24)); 

alert("diff " + diffDays);

This happens:

data final= 02/06/2010
data inicial = 08/06/2020

It says that final date cannot be less than initial date and returns false, this is correct. Now if

data final = 31/07/2020
data inicial = 08/06/2020

Returns an Nan in diffDays and does not validate a vacation period longer than 30. I’ve done the same thing with Math.floor. Math.abs does not validate anything.

Edit

There is an error that I have picked up now. When I give getDate() on the date, I should return the date day and is returning me the month. Maybe that’s the problem

Edit2

I switched to that

var inicioFerias = new Date($("#txtInitialVacancies").val().split("/"));
var fimFerias    = new Date($("#txtFinalVacancies").val().split("/"));
var dateStart = inicioFerias.toLocaleDateString();
var dateEnd = fimFerias.toLocaleDateString();


var dd = (Date.parse(dateEnd) - Date.parse(dateStart)) / (1000*60*60*24);
alert("qdt " + dd);

var diffDays = dd;

And I’ll take the next one. When the End Date is less than the Start Date, fine, it works, but when the End Date is greater than the Start Date, I get an Nan

Answer 1

If the date is in the format you reported 08/06/2020, then the problem is in the first lines, none of your implementations below is valid for dates:

var inicioFerias = new Date($("#txtInitialVacancies").val());
var inicioFerias = new Date($("#txtInitialVacancies").val().split("/"));

Do not work because the interface of new Date(data) expects a date in format:

new Date();//Atribui data e hora atual
new Date(ano, mês, dia, hora, minuto, segundo, milissegundo);
new Date(valor);//Inteiro em milisegundos
new Date(dataString);//String em alguns formato ISO-8601 (2020-06-08T00:00:00)

Reference: Documentation Date

You can change the date format in several ways, I would use regex:

var inicioFerias = new Date($("#txtInitialVacancies").val().replace(/(\d{2})\/(\d{2})\/(\d{4})/, "$3-$2-$1"));

If you find understanding complex can give revert + Join in your second solution:

var inicioFerias = new Date($("#txtInitialVacancies").val().split("/").reverse().join("-"));