Here you can find the source of addDays(date, days)
function addDays(date, days) { var result = new Date(date); result.setDate(date.getDate() + days); return result; }
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);
};
Date.prototype.addDays = function (days) { this.setDate(this.getDate() + days); return this; };
Date.prototype.addDays = function(days) { var date = new Date(this.valueOf()) date.setDate(date.getDate() + days); return date; };
Date.prototype.addDays = function(days) { const dat = new Date(this.valueOf()); dat.setDate(dat.getDate() + days); return dat; };
Date.prototype.addDays = function(days) var dat = new Date(this.valueOf()); dat.setDate(dat.getDate() + days); return dat;