Nodejs Year Calculate subYears(value)

Method Source Code

Date.prototype.subYears = function(value) {
   var month = this.getMonth();
   this.setFullYear(this.getFullYear() - value);

   if (month < this.getMonth()) {
      this.setDate(0);/*from   w  w w .j  av a 2s .  c  o m*/
   }

   return this;
};

Related

1. getYear()

   window = this;
   Date.prototype.getYear = function() {
     return new Date().getFullYear();
   };
   function Error(message, description) {
     const e = new Error(message);
     e.description = description;
     return e;
   

2. increaseYear(num)

   var weekdays = exports.weekdays = ["sunday", "monday", "tuesday", "wednesday", "thursday", "friday", "saturday"];
   Date.prototype.increaseYear = function(num) {
     this.setUTCFullYear(this.getUTCFullYear() + num);
   Date.prototype.increaseMonth = function(num) {
     var str = this.getUTCFullYear()+"-"+(this.getUTCMonth()+num + 1)+"-"+
           this.getUTCDate()+"T"+this.getUTCHours()+":"+this.getUTCMinutes()+":"+
           this.getUTCSeconds()+"."+this.getUTCMilliseconds()+"Z";
     var date = new Date(str);
   ...
   

3. isThisYear()

   Date.prototype.isThisYear = function() {
       return new Date().getYear() == this.getYear();
   };
   

4. toYearEnd()

   Date.prototype.toYearEnd = function () {
       var date = new Date(this);
       date.setMonth(12);
       date.setDate(0);
       return date;
   };
   

5. toYearStart()

   Date.prototype.toYearStart = function () {
       var date = new Date(this);
       date.setMonth(0);
       date.setDate(1);
       return date;
   };
   

6. weekOfYear()

   Date.prototype.weekOfYear = function () {
       var year = this.getFullYear();
       var d = new Date(this);
       d.setHours(0, 0, 0, 0);
       var yearStart = new Date(year, 0, 1);
       d.setDate(d.getDate() + yearStart.getDay());
       var deltaDay = (d.getTime() - yearStart.getTime()) / 86400000 + 1;
       var weekNo = Math.ceil(deltaDay / 7);
       return [year, weekNo];
   ...
   

7. yearStartDay()

   Date.prototype.yearStartDay = function(){
     return new Date(this.getFullYear(),0,1).getDay();