@mk-kit/validators

Zero-dependency validators for Polish and European identifiers. Pure TypeScript functions — usable in Angular, React, Node, a worker, a script — plus thin adapters for Angular reactive forms and Signal Forms. Every algorithm cites its source in the code and is covered by property tests (hundreds of generated values, single-digit errors caught).

npm install @mk-kit/validators

| Identifier | Functions | Checks | |---|---|---| | PESEL | isPesel, parsePesel → { birthDate, sex, serial } | weights 1-3-7-9, check digit, real calendar date, century from the month offset | | NIP | isNip, normalizeNip, formatNip | weights 6-5-7-2-3-4-5-6-7 mod 11; PL prefix, dashes and spaces tolerated | | REGON | isRegon | 9- and 14-digit variants, both check digits | | KRS | isKrs, normalizeKrs | 10 digits with zero padding (no check digit exists) | | ID card (dowód) | isPolishIdCard | letters A→10…, weights 7-3-1, control digit | | IBAN | isIban, parseIban, formatIban | ISO 7064 MOD 97-10, SWIFT registry lengths (88 countries) | | EU VAT | isVatId, parseVatId | VIES syntax for 27 states + XI, EL/GR, PL checksum | | Cards | isLuhn, isCardNumber, detectCardBrand | Luhn, IIN ranges, brand-valid lengths | | Postal codes | isPostalCode | 36 countries, separator optional | | Phones | isE164, toE164 | E.164 shape; national → international normalisation |

import { isNip, parsePesel, parseIban, toE164 } from '@mk-kit/validators';

isNip('PL 123-456-32-18');                    // true
parsePesel('44051401359');                    // { birthDate: 1944-05-14, sex: 'M', serial: '0135' }
parseIban('pl61 1090 1014 0000 0712 1981 2874')?.formatted; // 'PL61 1090 1014 0000 0712 1981 2874'
toE164('601 234 567', { defaultCountry: 'PL' }); // '+48601234567'

Every is* takes unknown and returns boolean; every parse* returns a typed object or null. Separators, case and surrounding whitespace are forgiven where the identifier allows it. Syntax validity is not registration: a VAT number still needs a VIES lookup, an IBAN still needs a bank.

Angular reactive forms

import { nipValidator, ibanValidator, postalCodeValidator } from '@mk-kit/validators/forms';

form = new FormGroup({
  nip: new FormControl('', [Validators.required, nipValidator()]),
  iban: new FormControl('', ibanValidator()),
  zip: new FormControl('', postalCodeValidator('PL')),
});

Empty values pass (compose with Validators.required). Errors are { nip: { value } }, { postalCode: { value, country } } and so on. The entry imports only types from @angular/forms — no runtime dependency.

Angular Signal Forms / Standard Schema

import { form, schema, validateStandardSchema } from '@angular/forms/signals';
import { nipSchema, peselSchema } from '@mk-kit/validators/signals';

const customer = schema<Customer>((p) => {
  validateStandardSchema(p.nip, nipSchema({ message: 'Nieprawidłowy NIP' }));
  validateStandardSchema(p.pesel, peselSchema());
});

Each schema is a plain Standard Schema v1 object, so it also works with any other library that accepts one. schemaFrom(predicate, message) wraps your own check the same way.

Related

• @mk-kit/ui — the Angular component library these checks grew out of (mk-tax-id-input, mk-iban-input, mk-postal-code-input, mk-phone-input).
• Docs: https://mk-kit.dev

MIT © Mateusz Kornaś