IBAN Validation in Angular

iban.validator.ts

const codeLengths: { [code: string]: number } = {
  AD: 24,
  AE: 23,
  AL: 28,
  AT: 20,
  AZ: 28,
  BA: 20,
  BE: 16,
  BG: 22,
  BH: 22,
  BR: 29,
  CH: 21,
  CR: 21,
  CY: 28,
  CZ: 24,
  DE: 22,
  DK: 18,
  DO: 28,
  EE: 20,
  ES: 24,
  LC: 30,
  FI: 18,
  FO: 18,
  FR: 27,
  GB: 22,
  GI: 23,
  GL: 18,
  GR: 27,
  GT: 28,
  HR: 21,
  HU: 28,
  IE: 22,
  IL: 23,
  IS: 26,
  IT: 27,
  JO: 30,
  KW: 30,
  KZ: 20,
  LB: 28,
  LI: 21,
  LT: 20,
  LU: 20,
  LV: 21,
  MC: 27,
  MD: 24,
  ME: 22,
  MK: 19,
  MR: 27,
  MT: 31,
  MU: 30,
  NL: 18,
  NO: 15,
  PK: 24,
  PL: 28,
  PS: 29,
  PT: 25,
  QA: 29,
  RO: 24,
  RS: 22,
  SA: 24,
  SE: 24,
  SI: 19,
  SK: 24,
  SM: 27,
  TN: 24,
  TR: 26,
};

export function ibanValidator(value: string) {
  if (!value) {
    return true;
  }

  const iban = value.toUpperCase().replace(/[^\dA-Z]/g, '');
  const code = iban.match(/^([A-Z]{2})(\d{2})([\dA-Z]+)$/);
  if (!code || iban.length !== codeLengths[code[1]]) {
    return false;
  }
  const digits = (code[3] + code[1] + code[2]).replace(/[A-Z]/g, (letter: string) => {
    // eslint-disable-next-line unicorn/prefer-code-point
    return letter.charCodeAt(0) - 55;
  });
  
  return mod97(digits) === 1;
}

function mod97(digital: number | string) {
  digital = digital.toString();
  let checksum: number | string = digital.slice(0, 2);
  let fragment = '';
  for (let offset = 2; offset < digital.length; offset += 7) {
    // eslint-disable-next-line unicorn/prefer-string-slice
    fragment = checksum + digital.substring(offset, offset + 7);
    checksum = Number(fragment) % 97;
  }
  return checksum;
}