#checksum code explainers

javascript

const IBAN_LENGTHS = {
  DE: 22, FR: 27, GB: 22, ES: 24, IT: 27,
  NL: 18, BE: 16, CH: 21, AT: 20, PT: 25,
};

How IBAN validation works in JavaScript

validation checksum modular-arithmetic

Intermediate 8 steps

typescript

export function isValidCardNumber(input: string): boolean {
  const digits = input.replace(/[\s-]/g, "");
 
  if (!/^\d{12,19}$/.test(digits)) {

Validating card numbers with the Luhn check

luhn-algorithm checksum input-validation

Intermediate 7 steps

ruby

module CreditCard
  module_function
 
  def valid?(number)

Validating credit card numbers with Luhn

checksum luhn-algorithm validation

Intermediate 6 steps

python

def is_valid_card_number(number: str) -> bool:
    digits = [int(c) for c in number if c.isdigit()]
 
    if len(digits) < 13 or len(digits) > 19:

Validating card numbers with the Luhn check

checksum validation luhn-algorithm

Intermediate 6 steps

javascript

function isValidCardNumber(input) {
  const digits = String(input).replace(/[\s-]/g, '');
 
  if (!/^\d{13,19}$/.test(digits)) {

Validating card numbers with Luhn

checksum validation luhn-algorithm

Intermediate 7 steps

java

public final class IbanValidator {
 
    private static final Map<String, Integer> COUNTRY_LENGTHS = Map.ofEntries(
        Map.entry("DE", 22), Map.entry("FR", 27), Map.entry("GB", 22),

Validating IBANs with the mod-97 checksum

validation checksum modular-arithmetic

Intermediate 8 steps