Nodejs Utililty Methods Day of Week

Date.prototype.dayOfWeek = function(){
  var days = ["Sunday", "Monday", "Tuesday", "Wednesday",
              "Thursday", "Friday", "Saturday"];
  return days[this.getDay()];

var weekday = new Array(7);
weekday[0] = "Sunday";
weekday[1] = "Monday";
weekday[2] = "Tuesday";
weekday[3] = "Wednesday";
weekday[4] = "Thursday";
weekday[5] = "Friday";
weekday[6] = "Saturday";
Date.prototype.getDayOfWeek = function() {
...

Date.prototype.getDayOfWeek = function(){   
    return ["Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday"][ this.getDay() ];
};
Date.prototype.getDayNum = function(){ 
    let day = this.getDay()
    if(day == 0) day = 7
    return day;
};

Date.prototype.getDayOfWeek = function() {
  var days = [
    "Sonntag",
    "Montag",
    "Dienstag",
    "Mittwoch",
    "Donnerstag",
    "Freitag",
    "Samstag"
...

Date.prototype.getDayOfWeek = function(d) {
  var days = ["Sun", "Mon", "Tue", "Wed", 
      "Thu", "Fri", "Sat"];
  return days[d];