공휴일 선택안되는 jQuery Datepicker 구현 (delayed render datepicker)

http://apis.data.go.kr/B090041/openapi/service/SpcdeInfoService/getRestDeInfo?serviceKey=[서비스키]&solYear=2022&solMonth=01&_type=json

{
  "response": {
    "header": { "resultCode": "00", "resultMsg": "NORMAL SERVICE." },
    "body": {
      "items": {
        "item": [
          { "dateKind": "01", "dateName": "설날", "isHoliday": "Y", "locdate": 20220201, "seq": 1 },
          { "dateKind": "01", "dateName": "설날", "isHoliday": "Y", "locdate": 20220202, "seq": 1 }
        ]
      },
      "numOfRows": 10,
      "pageNo": 1,
      "totalCount": 2
    }
  }
}

function applyHolidayPicker(ins) {
  var patchHolidays = (year, month, callback) => {
    if (('' + month).length == 1) month = '0' + month
    // 한국천문연구원_특일 정보
    // https://www.data.go.kr/data/15012690/openapi.do
    $.get(
      'https://jsonp.afeld.me/?url=' +
        encodeURIComponent(
          'http://apis.data.go.kr/B090041/openapi/service/SpcdeInfoService/getRestDeInfo?serviceKey=[서비스키]&solYear=' +
            year +
            '&solMonth=' +
            month +
            '&_type=json'
        ),
      (ret) => {
        //console.log('ret',ret.response.body);
        var holidays = []
        try {
          if (ret.response.body.items) {
            if (ret.response.body.totalCount == 1) {
              ret.response.body.items.item = [ret.response.body.items.item]
            }
            ret.response.body.items.item.forEach((item) => {
              holidays.push(item.locdate)
            })
          }
          if (callback) callback(true, holidays)
        } catch (e) {
          console.log(e.message)
          if (callback) callback(false)
        }
      }
    )
  }

  ins.datepicker({
    changeMonth: true,
    changeYear: true,
    beforeShowDay: (day) => {
      if (ins.data('loading')) return [false]
      var holidays = ins.data('holidays')

      if (holidays) {
        var cur = day.getDate()
        var exists = holidays.filter((item) => parseInt(('' + item).substring(6)) == cur)
        if (exists.length) {
          return [false, 'date-holiday']
        }
      }
      var result = []
      switch (day.getDay()) {
        case 0:
          result = [false, 'date-sunday']
          break
        case 6:
          result = [false, 'date-saturday']
          break
        default:
          result = [true]
          break
      }
      return result
    },
    onChangeMonthYear: (year, month, picker) => {
      //console.log('year',year);
      //console.log('month',month);
      ins.data('loading', true)
      $(picker.dpDiv).css({ opacity: 0.5 })
      patchHolidays(year, month, (success, holidays) => {
        ins.data('loading', false)
        ins.data('holidays', holidays)
        $(picker.dpDiv).css({ opacity: 1 })
        //console.log('refresh');
        ins.datepicker('refresh')
      })
    },
    beforeShow: (input, picker) => {
      console.log('beforeShow')
      ins.data('loading', true)
      var curdate = new Date()
      patchHolidays(curdate.getFullYear(), curdate.getMonth() + 1, (success, holidays) => {
        ins.data('loading', false)
        ins.data('holidays', holidays)
        //console.log('refresh');
        ins.datepicker('refresh')
      })
    },
    onClose: () => {},
  })
}

applyHolidayPicker($('#date1'))