Nodejs Utililty Methods Day Add

Date.prototype.AddDays = function(amount) {
   var d = new Date(this.getTime());
   d.setDate(this.getDate() + amount);
   return d;
};

Date.prototype.AddDays = function (days) {
  this.setDate(this.getDate() + parseInt(days));
  return this.getFullYear() + "-" + (((this.getMonth()+1) < 10)?"0":"") + (this.getMonth()+1) +"-"+ ((this.getDate() < 10)?"0":"") + this.getDate();

Date.prototype.addDay = function(){
  this.setDate(this.getDate() + 1);
};

Date.prototype.addDay = function(day) {
  if (null == day || isNaN(day)) {
    return this;
  this.setDate(this.getDate() + day);
  return this;
};

Date.prototype.addDay = function addDay () {
  var day = this.getDate();
  this.setDate(day + 1);
  this.setHours(0);
  this.setMinutes(0);
  this.setSeconds(0);
  if (this.getDate() === day) {
    this.setDate(day + 2);
};

Date.prototype.addDays = function (d) {
    if (d) {
        var t = this.getTime();
        t = t + (d * 86400000);
        this.setTime(t);
        return this;
};

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

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

Date.prototype.addDays = function(d) {
  this.setDate(this.getDate() + d);
};
Date.prototype.addWeeks = function(w) {
  this.addDays(w * 7);
};
Date.prototype.addMonths = function(m) {
  var d = this.getDate();
  this.setMonth(this.getMonth() + m);
...

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