DNI/NIF validators (Spain ID documents)

spanish_dni_nif_validator.js

/* Return sum of numbers in array xs */
function sum(xs) {
  return xs.reduce(function(a, b) { return a + b }, 0);
}

/* Return true if string s is a valid DNI */
function validateDNI(s) {
  var control_letters = 'TRWAGMYFPDXBNJZSQVHLCKE';
  var regexp = /^[\dKLMXYZ]\d{7}[A-Z]$/;
  
  if (!s.match(regexp)) {
    return false;
  } else {
    var control_letter = s[s.length-1];
    var digits = s.match(/\d+/)[0]
    var expected_control_digit = parseInt(digits) % 23;
    var expected_control_letter = control_letters[expected_control_digit];
    return (control_letter == expected_control_letter);
  } 
}

/* Return true if string s is a valid NIF */
function validateNIF(s) {
  var regexp = /^[A-Z]\d{7}[A-Z0-9]$/;
  var control_letters = 'JABCDEFGHI';
  var validation = {with_digit: 'ABCDEFGHJUV', with_letter: 'NPQRSW'};
  
  if (!s.match(regexp)) {
    return false;
  } else {
    var code = s[0];
    var digits = s.slice(1, -1);
    var control_char = s[s.length - 1];
    var control_digit_values = digits.split('').map(function(digit, idx) {
      if ((idx + 1) % 2 == 0) {
          return parseInt(digit);
        } else {
          var digits_of_double = (2 * parseInt(digit)).toString().split('');
          return sum(digits_of_double.map(function(c) { return parseInt(c) }));
        }
    });
    var expected_control_digit = (10 - (sum(control_digit_values) % 10)) % 10;
    
    if (validation.with_digit.indexOf(code) >= 0) {
      return control_char == expected_control_digit;
    } else if (validation.with_letter.indexOf(code) >= 0) {
      return control_char == control_letters[expected_control_digit];
    } else {
      return false;
    }
  }
}

/* Return true if Spanish DNI or NIF validate */
function validateID(s) {
  return validateDNI(s) || validateNIF(s);
}