Nodejs Utililty Methods Day of Year

Date.prototype.dayOfYear = function() {
   var startdayofyear = new Date(this.getFullYear(),0,1);
  return Math.ceil((this - startdayofyear) / 86400000);

Date.prototype.dayOfYear = function() {
  var d = new Date(); 
  var yn = d.getFullYear();
  var mn = d.getMonth();
  var dn = d.getDate();
  var d1 = new Date(yn,0,1,12,0,0); 
  var d2 = new Date(yn,mn,dn,12,0,0); 
  var ddiff = Math.round((d2-d1)/864e5);
  return ddiff+1; 
...

Date.prototype.getDOY = function() {
  var onejan = new Date(this.getFullYear(),0,1);
  return Math.ceil((this - onejan) / 86400000);

Date.prototype.getDOY = function(){
  var firstOfJan = new Date(this.getFullYear(),0,1);
  return Math.ceil((this - firstOfJan) / 86400000);

Date.prototype.getDOY = function() {
    var dayCount = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
    var mn = this.getMonth();
    var dn = this.getDate();
    var dayOfYear = dayCount[mn] + dn;
    if (mn > 1 && this.isLeapYear()) dayOfYear++;
    return dayOfYear;
};

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Date.prototype.getDOY = function() {
  var onejan = new Date(this.getFullYear(),0,1);
  return Math.ceil((this - onejan) / 86400000);

Date.prototype.getDOY = function () {
    var onejan = new Date(this.getFullYear(), 0, 1);
    return Math.ceil((this - onejan) / 86400000) + 1;
};

Date.prototype.getDayOfYear = function() {
  const janFirst = new Date(this.getFullYear(), 0, 0);
  const diff = this - janFirst;
  const millisPerDay = 86400000;
  return Math.floor(diff / millisPerDay);
};

Date.prototype.getDayOfYear = function () {
    var num = 0;
    Date.daysInMonth[1] = this.isLeapYear() ? 29 : 28;
    for (var i = 0; i < this.getMonth(); ++i) {
        num += Date.daysInMonth[i];
    return num + this.getDate() - 1;

Date.prototype.getDayOfYear = function() {
  var dayMs = 24 * 60 * 60 * 1000;
  var janFirst = new Date(this.getFullYear(),0,1);
  var date = new Date(this.getFullYear(), this.getMonth(), this.getDate(), 2)
  return Math.ceil((date-janFirst) / dayMs);
};