JavaScript Function to Format Currency (Money)

I am going to be posting a series of useful JavaScript functions for form validation and input formatting. This is the first in that series: a function which formats a number as currency.

function formatCurrency(num) 

{

	num = num.toString().replace(/\$|\,/g,'');

	if(isNaN(num)) num = "0";

	sign = (num == (num = Math.abs(num)));

	num = Math.floor(num*100+0.50000000001);

	cents = num%100;

	num = Math.floor(num/100).toString();

	if(cents<10) cents = "0" + cents;	

	return (((sign)?'':'-') + num + '.' + cents);

}