JavaScript: Date() helpers + paddingLeft()

date_helpers.js

/**
 * Pads string or number with symbols
 * @param  {string} paddingValue Padding string. E.g., "0000"
 * @return {string}              E.g., "0032"
 */
String.prototype.paddingLeft = function (paddingValue)
{
   return String(paddingValue + this).slice(-paddingValue.length);
};
/**
 * Formats date to "DD.MM.YY" format
 * @param  {string} separator Optional separator. Default value: "."
 * @return {string}           Formatted date
 */
Date.prototype.ddmmyy = function(separator)
{
	if (!separator) { separator = '.'; }
	var dateComponents = [
		this.getDay().toString().paddingLeft("00"),
		(this.getMonth()+1).toString().paddingLeft("00"),
		year = this.getFullYear().toString().substr(-2)
	];
	return dateComponents.join(separator);
};
/**
 * Formats date to "DD.MM.YYYY" format
 * @param  {string} separator Optional separator. Default value: "."
 * @return {string}           Formatted date
 */
Date.prototype.ddmmyyyy = function(separator)
{
	if (!separator) { separator = '.'; }
	var dateComponents = [
		this.getDay().toString().paddingLeft("00"),
		(this.getMonth()+1).toString().paddingLeft("00"),
		year = this.getFullYear().toString()
	];
	return dateComponents.join(separator);
};
/**
 * Formats date to "YYYY-MM-DD" format
 * @param  {string} separator Optional separator. Default value: "-"
 * @return {string}           Formatted date
 */
Date.prototype.yyyymmdd = function(separator)
{
	if (!separator) { separator = '-'; }
	var dateComponents = [
		year = this.getFullYear().toString(),
		(this.getMonth()+1).toString().paddingLeft("00"),
		this.getDay().toString().paddingLeft("00")
	];
	return dateComponents.join(separator);
};
/**
 * Returns Date object which is numDays days ahead of original date
 * @param  {int}	numDays	Optional number of days. Default value: 1
 * @return {Date}
 */
Date.prototype.nextDay = function(numDays)
{
	if (!numDays) { numDays = 1; }
	return new Date(this.getTime() + numDays * 24 * 60 * 60 * 1000);
};