Javascript Jquery datepicker addclass（）不工作

我有一个jquery datepicker addClass方法没有在id为#ui datepicker div的div中添加类

Jquery代码：

$(document).ready(function () {

      //this works
     $('.date-picker1').addClass("mtp");
          //This does not work
     $("#ui-datepicker-div").addClass("myclassdoesntgo");
     $('.date-picker1').datepicker({
         changeMonth: true,
         changeYear: true,
         showButtonPanel: true,
         dateFormat: 'yy',
         onClose: function (dateText, inst) {
             var month = 1;
             // month= $("#ui-datepicker-div .ui-datepicker-month :selected").val();
             var year = 1900;
             year = $("#ui-datepicker-div .ui-datepicker-year :selected").val();
             $(this).datepicker('setDate', new Date(year, 25));
             // $("startDate").val = month;
             $("startMonth").val = year;
         }
     });
     $('#ui-datepicker-div').css('display', 'none');

 });

---

完整代码是

只需在调用datepicker方法后添加它：

 $(document).ready(function () {

            $('.date-picker1').addClass("mtp");

            $('.date-picker1').datepicker({
                changeMonth: true,
                changeYear: true,
                showButtonPanel: true,
                dateFormat: 'yy',
                onClose: function (dateText, inst) {
                    var month = 1;
                    // month= $("#ui-datepicker-div .ui-datepicker-month :selected").val();
                    var year = 1900;
                    year = $("#ui-datepicker-div .ui-datepicker-year :selected").val();
                    $(this).datepicker('setDate', new Date(year, 25));
                    // $("startDate").val = month;
                    $("startMonth").val = year;
                }
            });
      $("#ui-datepicker-div").addClass("myclassdoesntgo");
      $('#ui-datepicker-div').css('display','none');

        }); 

---

这里的完整工作小提琴：

什么是

ui日期选择器div

？它是由日期选择器生成的id