CreditCard = cleanNumber: (number) -> number.replace /[- ]/g, "" validNumber: (number) -> total = 0 number = @cleanNumber(number) for i in [(number.length-1)..0] n = +number[i] if (i+number.length) % 2 == 0 n = if n*2 > 9 then n*2 - 9 else n*2 total += n total % 10 == 0 jQuery -> $("#order_credit_card_number").blur -> if CreditCard.validNumber(@value) $("#credit_card_number_error").text("") else $