Calling a web service from Jquery

Also uncomment the following code to run the code without error

// To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. 

 [System.Web.Script.Services.ScriptService]

 https://www.c-sharpcorner.com/blogs/how-to-call-asp-net-web-service-using-jquery-ajax

or 

 $.ajax({

        type: "POST",

        contentType: "application/json; charset=utf-8",

        url: '../DashboardReports/DashboardReports.aspx/GetUnderInvStats',

        data: JSON.stringify(reg),

        dataType: "json",

        success: function (data) {

            

            var html = '<table id="tblStatsMonthlyProgressReport1" class="table-striped table-bordered table-responsive-sm text-center display nowrap table-sm" style="width: 100%">';

            html += '<thead>';

            html += '<tr class="th_PendUT table" >';

            html += '<th scope="col" class="text-center">' + 'Sr.No.' + '</td>';

            html += '<th scope="col">' + 'Zone' + '</td>';

            html += '<th scope="col">' + 'Branch' + '</td>';

            html += '<th scope="col" class="text-center">' + 'Cases' + '</td>';

            html += '</tr>';

            html += '</thead>';

            $.each((data.d), function (key, value) {

                html += '<tr>';

                html += '<td>' + parseInt(key + 1) + '</td>';

                html += '<td class="text-start">' + value.Zone + '</td>';

                html += '<td class="text-start">' + value.Branch + '</td>';

                html += '<td>' + value.Cases + '</td>';

                html += '</tr>';

            });

            html += '</table>';

            document.getElementById('divStatsMPR1Container').innerHTML = html;

            var tbltitle = $("#ddlZone option:selected").html();

            var tblSubtitle = "Monthly Performance report Stats for the period from " + ($('#txtdateFrom').val()) + ' to ' + ($('#txtdateTo').val());

            $("[id$=divStatsMPR1Container]").show(500, BuildDataTableCommon($('#tblStatsMonthlyProgressReport1'), tbltitle, tblSubtitle));

            $('#model').hide();

        },

        error: function (response) {

            alert(response.responseText);

            $('#model').hide();

        }, complete: function (s, e) {

            alert("it is done");

        }

    });

ref:- https://stackoverflow.com/questions/19411580/postback-during-an-ajax-call