[jsgrid] json datetime column convert to javascript datetime on with custum format

var defaultFields = [
  { name: "Title", type: "text", width: "", title: "용어명", css: "text-left col-md-9 col-sm-9 col-xs-9" },
  { name: "RegisterId", type: "text", width: "", title: "등록자", css: "text-center col-md-1 col-sm-1 col-xs-1" },
  { name: "RegistDate", type: "date", width: "", title: "등록일시", css: "text-center col-md-1 col-sm-1 col-xs-1" },
  { name: "UseYn", type: "text", width: "", title: "사용유무", css: "text-center col-md-1 col-sm-1 col-xs-1" }
];

var DateField = function (config) {
  jsGrid.Field.call(this, config);
};

DateField.prototype = new jsGrid.Field({
  itemTemplate: function (value) {
    return new Date(value.match(/\d+/)[0] * 1).format("yyyy-MM-dd");
  }
});

jsGrid.fields.date = DateField;
$(function () {
  var formCollection = $("#termForm").serialize();
  $("#btnRegist").on("click", function () {
    location.replace("/Term/TermRegist");
  });
});

$("#jsGrid").jsGrid({
  width: "100%",
  height: "auto",
  inserting: false,
  editing: false,
  sorting: true,
  heading: true,
  paging: true,
  pageSize: 10,
  pageButtonCount: 10,
  pagerContainer: "#externalPager",
  pagerFormat: "{first} {prev} {pages} {next} {last}",
  pagePrevText: "<span class=\"lightblue\"><</span>",
  pageNextText: ">",
  pageFirstText: "<<",
  pageLastText: ">>",
  pageNavigatorNextText: "&#8230;",
  pageNavigatorPrevText: "&#8230;",
  controller: {
    loadData: function (filter) {
    return $.ajax({
    type: "GET",
    url: "/Term/TermListForJson",
    data: filter,
    dataType: "JSON"
    })
  }
},
fields: defaultFields,
onPageChanged: function (args) {
  $("input[name=pageNo]").val(args.pageIndex);
},
rowClick: function (args) {
  location.replace("/Term/TermView/" + args.item.TermNo);
}
});

Date.prototype.format = function (f) {
  if (!this.valueOf()) return " ";
  var weekName = ["일요일", "월요일", "화요일", "수요일", "목요일", "금요일", "토요일"];

  var d = this;
  return f.replace(/(yyyy|yy|MM|dd|E|hh|mm|ss|a\/p)/gi, function ($1) {
    switch ($1) {
      case "yyyy": return d.getFullYear();
      case "yy": return (d.getFullYear() % 1000).zf(2);
      case "MM": return (d.getMonth() + 1).zf(2);
      case "dd": return d.getDate().zf(2);
      case "E": return weekName[d.getDay()];
      case "HH": return d.getHours().zf(2);
      case "hh": return ((h = d.getHours() % 12) ? h : 12).zf(2);
      case "mm": return d.getMinutes().zf(2);
      case "ss": return d.getSeconds().zf(2);
      case "a/p": return d.getHours() < 12 ? "오전" : "오후";
      default: return $1;
    }
  });
};

String.prototype.string = function (len) { var s = '', i = 0; while (i++ < len) { s += this; } return s; };
String.prototype.zf = function (len) { return "0".string(len - this.length) + this; };
Number.prototype.zf = function (len) { return this.toString().zf(len); };