I don't know wht kind of checker you're talking about but for reference, this is just a basic checker that will take a card number as input and check its validity using the Luhn algorithm but you get the point. It will also check if the card has expired.
function check_card(card_number, exp_date):
// Remove any spaces or hyphens from the card number
card_number = card_number.replace(" ", "").replace("-", "")
// Check if the card number has 16 digits
if len(card_number) != 16:
return "Invalid card number length"
// Check if the card number is a valid credit card number using Luhn algorithm
if not luhn_check(card_number):
return "Invalid card number"
// Check if the card has expired
if exp_date < current_date():
return "Card has expired"
return "Card is valid"
function luhn_check(card_number):
sum = 0
for i in range(len(card_number) - 1, -1, -2):
digit = int(card_number
)
digit *= 2
if digit > 9:
digit -= 9
sum += digit
for i in range(len(card_number) - 2, -1, -2):
sum += int(card_number)
return sum % 10 == 0
Algorithm:
Remove any spaces or hyphens from the card number.
Check if the card number has 16 digits. If not, return "Invalid card number length".
Check if the card number is a valid credit card number using the Luhn algorithm. If not, return "Invalid card number".
Check if the card has expired by comparing the expiration date with the current date. If it has expired, return
"Card has expired".
If all checks pass, return "Card is valid".
thua luhn_check function implements the Luhn algorithm, which is used to validate credit card numbers:
Start from the rightmost digit and double every second digit.
If the result is a two-digit number, subtract 9 from it.
Add up all the digits.
If the total is a multiple of 10, the card number is valid. Otherwise, it's invalid.
