Nodejs Utililty Methods Day Calculate

Date.prototype.getStartOfDay = function()
    var date = new Date(this);
    date.setHours(0);
    date.setMinutes(0);
    date.setSeconds(0);
    return date;

'use strict';
Date.prototype.getThisDay = function()
    var date = new Date();
    return [date.setHours(0,0,0,0), date.setHours(23,59,59,999)];

Date.prototype.getToday = function () {
    return this.getFullYear()+'-'+this.getMonth()+'-'+this.getDate();

Date.prototype.getToday = function () {
    return this.getFullYear()+'-'+this.getMonth()+'-'+this.getDate();

Date.prototype.isDST = Date.prototype.isDST || function() { 
    var jan = new Date(this.getFullYear(),0,1);
    var jul = new Date(this.getFullYear(),6,1);
    return Math.min(jan.getTimezoneOffset(),jul.getTimezoneOffset()) == this.getTimezoneOffset();
};
exports.DataUtilities = {};

Date.prototype.isLastDay = function(){
    if(!this.isToDay()){
        var today = new Date();
        return this.getTime() < today.getTime();
    return false;
};

Date.prototype.nextDay = funciton() {
  let today = this.getDate();
  return new Date(this.setDate(today + 1));

Date.prototype.numDays = function() {
  var d = new Date(this.getFullYear(), this.getMonth() + 1, 0);
  return d.getDate();
};

Date.prototype.past = function(pattern,pastDays){
    var pastday = new Date((this - 0) - 1000*60*60*24*pastDays);
    var pattern = pattern;    
    var dateObj = {
        "Y" : pastday.getFullYear(),
        "M" : pastday.getMonth()+1,
        "D" : pastday.getDate(),
        "h" : pastday.getHours(),
        "m" : pastday.getMinutes(),
...

Date.prototype.relativeDays = function() {
  var now = new Date();
  var interval = now.getTime() - this.getTime();
  interval = Math.floor(interval / (1000 * 60 * 60 * 24));
  return interval;
};