JQuery DateTimePicker在 Select 中抓取星期几

$("input.date").datepicker({
  onSelect: function(dateText, inst) {
    $("#" + this.id + "_changeTime").val(Date.now()).trigger('change');

    var currentDate = $(this).datepicker("getDate");

    var days = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];
    var months = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

    var day = days[currentDate.getDay()];
    var month = months[currentDate.getMonth()];

    $("#" + this.id + "_day").attr("value", day);
    $("#" + this.id + "_month").attr("value", month);

    var options = {
      weekday: 'long',
      year: 'numeric',
      month: 'long',
      day: 'numeric',
      hour: '2-digit',
      minute: '2-digit',
      second: '2-digit',
      hour12: false
    };
    $("#" + this.id + "_date").attr("value", currentDate.toLocaleTimeString('en-us', options));
  },
  changeMonth: true,
  changeYear: true,
  yearRange: '1900:2050',
  showButtonPanel: true,
  showOn: 'both',
  buttonText: 'Date',
  buttonImageOnly: true,
  closeText: 'Close',
  showAnim: '',
  dayNamesShort: true
});

<link href="//cdnjs.cloudflare.com/ajax/libs/jqueryui/1.11.4/jquery-ui.css" rel="stylesheet" />

<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.2.4/jquery.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jqueryui/1.11.4/jquery-ui.js"></script>

<input class='date' id='dt'>
<input id='dt_month'>
<input id='dt_day'>
<input id='dt_date'>
<input id='dt_changeTime'>