Validerar svenska personnummer. Kollar längd, att det är ett giltigt datum samt validerar checksumman.

validatePersonnummer.js

(function (exports) {
  function validatePersonnummer (personnummer) {
    // Ensure string in case of number
    personnummer = "" + personnummer;

    // Trim non-digits
    // This discards (and thus accepts) any non-digits anywhere in the personnummer.
    // Depending on your case, that might not be the desired behavior.
    personnummer = personnummer.replace(/[^\d]/g, '');

    // Return true if both a valid date and has a valid checksum
    return hasValidLength(personnummer) &&
      hasValidDate(personnummer) &&
      hasValidChecksum(personnummer);
  }

  function hasValidLength (personnummer) {
    // Ensure there's 10 or 12 digits
    return personnummer.length === 10 || personnummer.length === 12;
  }

  function hasValidDate (personnummer) {
    var date, year, month, day;

    // Pad it to 12 digits so we have a real year
    if(personnummer.length === 10) {
      personnummer = '19' + personnummer;
    }

    // Extract year/month/date and convert to number
    year = +personnummer.substring(0, 4);
    month = +personnummer.substring(4, 6) - 1; // Js-month is one less
    day = +personnummer.substring(6, 8);

    date = new Date(year, month, day);

    if(!+date) {
      return false;
    }

    // Now test that no year/month/day has overflowed. If it has, the date was invalid
    return year === date.getFullYear() &&
      month === date.getMonth() &&
      day === date.getDate();
  }

  function hasValidChecksum (numbers) {
    var n, i, l,
        checksum = 0;

    // Accept a 12-length personnummer, but always start with the two last digits
    // of the year
    for(i = numbers.length - 10, l = numbers.length; i < l; i++) {
      n = +numbers[i];

      if(i % 2 === 0) {
        checksum += (n * 2) % 9 + ~~(n / 9) * 9;
      }
      else {
        checksum += n;
      }
    }

    return checksum % 10 === 0;
  }

  // Some hack to support both node and browsers
  exports = validatePersonnummer;
}(typeof module !== 'undefined' && module.exports || window.validatePersonnummer));