AJAX parameter for MVC not equal to NULL?

Question

I have a drop-down list where I can choose a location to filter my data.

I have an array that I send to the controller with AJAX. On my local computer, I get the parameter equal to zero if I did not select any of the drop-down list, as expected. However, on my website, it looks like the variable is not null because it is requesting data, so the result is empty.

How can it be? I want the value to be zero, so I can filter the data correctly.

Thanks Stefan

JQuery

$("#main").on("click", "#submit-search-catalog", function () {
    var url = "/Home/Catalog";

    var locations = $("#County").val();

    if (url != "") {
        $.post(url, { locations: locations },
        function (data) {
            if (data) {
                $(".catalog-container").html(data);
            }
        }).fail(function (xhr, status, error) {
            alert("Error");
        });
    }

    return false;
});

MVC controller

    public async Task<ActionResult> Catalog(int[] locations = null)
    {

        var companies = await db.Users.Where(u => u.IsVisibleInCatalog.Equals(true)).OrderBy(u => u.CompanyRegistrationDate).ToListAsync();

        //Sort locations
        if (!(locations == null || locations.Length == 0))
        {
            companies = companies.Where(c => locations.Contains(c.CompanyLocation) || c.CompanyLocation.Equals(1)).ToList();
        }

        var model = new CatalogViewModel
        {
            Companies = companies
        };

        if (Request.IsAjaxRequest())
        {
            return PartialView("~/Views/Home/_CatalogListPartial.cshtml", companyList);
        }

        return View(model);
    }

- EDIT

I tried this for error testing, and locally it alerts “empty” and serveride it warns “null”:

    if (locations == null)
        alert("null");

    if (locations.length == 0)
        alert("empty");

Answer 1

jquery . $( "# " ) (); . val(); jQuery 3.0, , ; jQuery 3.0 null. , , .

Answer 2

script. :

if (url != "")

:

 if (url !== "")