Regular Expression to Format Currency In Javascript

gistfile1.txt

    function formatCurrency(amount)
    {
      //truncate the amount to 0 decimals
      //for every digit that is followed by 3 digits and a word boundary
      //add a comma
			amount = amount.toFixed(0).replace(/(\d)(?=(\d{3})+\b)/g, "$1,");
			return amount;
	  }