Nodejs Utililty Methods Day in Month

Date.prototype.daysInMonth = function() {
    return 32 - new Date(this.getFullYear(), this.getMonth(), 32).getDate();
};

Date.prototype.daysInMonth = function() {
    return 32 - new Date(this.getYear(), this.getMonth(), 32).getDate();
};

dateFormat.i18n = {
  dayNames: [
    "Dom", "Lun", "Mar", "Mie", "Jue", "Vie", "Sab",
    "Domingo", "Lunes", "Jueves", "Mi?oles", "Jueves", "Viernes", "S?do"
  ],
  monthNames: [
    "Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
    "Enero", "Febrero", "Marzo", "Abril", "Mayo", "Junio", "Julio", "Agosto", "Septiembre", "Octubre", "Noviembre", "Diciembre"
  ]
...

Date.prototype.daysInMonth = function () {
  return new Date(this.getFullYear(), this.getMonth() + 1, 0).getDate();
};

Date.prototype.getDaysInMonth = function () {
    var here = new Date(this.getTime());
    here.setDate(32);
    return 32 - here.getDate();
};

Date.prototype.getDaysInMonth = function () {
    Date.daysInMonth[1] = this.isLeapYear() ? 29 : 28;
    return Date.daysInMonth[this.getMonth()];

Date.prototype.getDaysInMonth = function() {
  return Date.getDaysInMonth(this.getFullYear(), this.getMonth());
};

Date.prototype.getDaysInMonth = function ()
    return Date.getDaysInMonth(this.getFullYear(), this.getMonth());
};

Date.prototype.getDaysInMonth = function () {
    var m = this.getMonth() + 1,
        y = this.getFullYear();
    return /8|3|5|10/.test(--m) ? 30 : m == 1 ? (!(y % 4) && y % 100) || !(y % 400) ? 29 : 28 : 31;
};

Date.getDaysInMonth = function(year, month) {
  return [
    31, (Date.isLeapYear(year) ? 29 : 28),
    31, 30, 31, 30, 31, 31, 30, 31, 30, 31
  ][month];
};