A simple helper method to get the days of week

getWeekDayString.js

(function(Date) {
  
  if (new RegExp(Date.name).test(Object.prototype.toString.call(new Date)) && !Date.prototype.getWeekDayString) {
    const WEEKDAYS = ["SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"];
    Date.prototype.getWeekDayString = function() {
      return WEEKDAYS[this.getDay()];
    };
  }
})(globalThis && globalThis.Date || (window && window.Date || global && global.Date));