Nodejs Utililty Methods Day Add

'use strict';
Date.prototype.addDays = function(days) {
  var date = new Date(this.valueOf());
  date.setDate(date.getDate() + days);
  return date;

Date.prototype.addDays = function (days) {
   days = this.getDate() + days;
   return this.setDate(days);
};

Date.prototype.addDays = function(days){
    var r = this.valueOf();
    r += 86400000 * days;
    return  new Date(r);
};

Date.prototype.addDays = function(days) {
  var d = new Date(this.valueOf());
  d.setDate(d.getDate() + days);
  return d;
};

Date.prototype.addDays = function(days){
  return new Date(this.getTime() + days*24*60*60*1000);

Date.prototype.addDays = function (days) {
    var date = new Date(this.valueOf());
    date.setDate(date.getDate() + days);
    return date;

var month = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
Date.prototype.addDays = function (days) {
    this.setDate(this.getDate() + days);
};
function isNumber(n) {
    return !isNaN(parseFloat(n)) && isFinite(n);
function CurrencyFormatted(amount) {
    var i = parseFloat(amount), minus = '', s;
...

Date.prototype.addDays = function(days) {
    this.setDate(this.getDate()+days);

Date.prototype.addDays = function (days) {
    var dat = new Date(this.valueOf());
    dat.setDate(dat.getDate() + days);
    return dat;
};
function getDateOfISOWeek(w, y) {
    var simple = new Date(y, 0, 1 + (w - 1) * 7);
    var dow = simple.getDay();
    var ISOweekStart = simple;
...

Date.prototype.addDays = function (days) {
    var date = new Date(this.valueOf());
    date.setDate(date.getDate() + days);
    return date;
};