function formatCurrency(num) {
	num = (num || '0').toString().replace(/\$|\,/g, '');
	if (isNaN(num)) num = "0";
	if (num + 0 == 0) return '$0';
	
	var sign = (num == (num = Math.abs(num)));
	num = Math.floor(num * 100 + 0.50000000001);
	
	var cents = num % 100;
	num = Math.floor(num / 100).toString();
	
	if (cents < 10) cents = "0" + cents;
	
	return [
		sign ? '' : '-',
		'$',
		Number.format(num),
		'.',
		cents
	].join('');
}

Number.prototype.format = function(separator){
	separator = separator || ',';
	var num = String(this);
	for (var i = 0; i < Math.floor((num.length - (1 + i)) / 3); i++)
		num = num.substring(0, num.length - (4 * i + 3)) + separator + num.substring(num.length - (4 * i + 3));
	return num;
};

Number.format = function(num, separator){
	return Number.prototype.format.call(num, separator);
};