asp.net core getting data from json and jquerry

Question

I have two select and I want to populate the second but I don't know what am I doing wrong

<div class="col-md-10 mb-2">
    <select id="IRSelect" class="form-control ml-1">
        <option value="">--Select Filtering Condition--</option>
        <option value="1">Issuer</option>
        <option value="2">Receiver</option>
    </select>
</div>
<div class="col-md-10">
    <select id="IRDetail" class="form-control ml-1" asp-items="@(new SelectList(string.Empty, "Issuer", "Issuer"))">
        <option value="">--Select Name--</option>
    </select>
</div>

and json

public async Task OnGetIRDetails1Async()
{
    var userId = User.FindFirstValue(ClaimTypes.NameIdentifier);
    var orgid = await _context.UsersData.Where(s => s.Id == userId).Select(s => s.OrgID).FirstOrDefaultAsync();
    var todayYear = DateTime.Today.Year;
    var valIR = await _context.PTWContents.Where(s => s.OrgID == orgid && s.StartDate.Year == todayYear).Select(s =>
                                new SelectListItem
                                {
                                    Value = s.Issuer,
                                    Text = s.Issuer
                                }).ToListAsync();

    return new JsonResult(new SelectList(valIR , "Issuer", "Issuer"));
}
public async Task OnGetIRDetails2Async()
{
    var userId = User.FindFirstValue(ClaimTypes.NameIdentifier);
    var orgid = await _context.UsersData.Where(s => s.Id == userId).Select(s => s.OrgID).FirstOrDefaultAsync();
    var todayYear = DateTime.Today.Year;
    var valIR = await _context.PTWContents.Where(s => s.OrgID == orgid && s.StartDate.Year == todayYear).Select(s =>
                                new SelectListItem
                                {
                                    Value = s.Receiver,
                                    Text = s.Receiver
                                }).ToListAsync();

    return new JsonResult(new SelectList(valIR , "Receiver", "Receiver"));
}

and jquery

$(function () {
    $("#IRSelect").on("change", function () {
        var categoryId = $(this).val();

        if (categoryId = 1) {
            $("#IRDetail").empty();
            $("#IRDetail").append("<option value=''>--Select Name--</option>");
            $.getJSON(`?handler=IRDetails1`, (data) => {
                $.each(data, function (i, item) {
                    $("#IRDetail").append(`<option value="${item.value}"> ${item.text}</option>`);
                });
            });
        }
        if (categoryId = 2) {
            $("#IRDetail").empty();
            $("#IRDetail").append("<option value=''>--Select Name--</option>");
            $.getJSON(`?handler=IRDetails2`, (data) => {
                $.each(data, function (i, item) {
                    $("#IRDetail").append(`<option value="${item.value}"> ${item.text}</option>`);
                });
            });
        }

    });
});