Nodejs Utililty Methods Day Add

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

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

Date.prototype.addDays = function(days)
    this.addMilliseconds(days * 24 * 3600 * 1000);
    return this;
};

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

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

Date.prototype.addDays = function (dias){
      var fecha1 = new Date(2011, 1,20);
      var fecha2 = new Date(2011, 1,21);
      var diferencia = fecha2.getTime() - fecha1.getTime();
      var luego = new Date();
      luego.setTime( this.getTime() + (dias * diferencia )  );
      return luego;

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

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

'use strict';
Date.prototype.nextDay = function() {
  var currentDate = this.getDate();
  console.log('currentDate', currentDate);
  return new Date(this.setDate(currentDate + 1));
var d = new Date();
console.log('Next day', d.nextDay());

Date.prototype.nextDay = function(){
  let currentDate = this.getDate();
  return new Date(this.setDate(currentDate + 1));
let date = new Date();
console.log(date);
console.log(date.nextDay());