gistfile1.js

var CreditCard = {
  CARDS: {
    Visa: /^4[0-9]{12}(?:[0-9]{3})?$/,
    MasterCard: /^5[1-5][0-9]{14}$/,
    DinersClub: /^3(?:0[0-5]|[68][0-9])[0-9]{11}$/,
    Amex: /^3[47][0-9]{13}$/,
    Discover: /^6(?:011|5[0-9]{2})[0-9]{12}$/
  },
  TEST_NUMBERS: $w('378282246310005 371449635398431 378734493671000 '+
    '30569309025904 38520000023237 6011111111111117 '+
    '6011000990139424 5555555555554444 5105105105105100 '+
    '4111111111111111 4012888888881881 4222222222222'
  ),
  validate: function(number){
    return CreditCard.verifyLuhn10(number)
      && !!CreditCard.type(number)
      && !CreditCard.isTestNumber(number);
  },
  verifyLuhn10: function(number){
    return ($A(CreditCard.strip(number)).reverse().inject(0,function(a,n,index){
      return a + $A((parseInt(n) * [1,2][index%2]).toString())
        .inject(0, function(b,o){ return b + parseInt(o) }) }) % 10 == 0);
  },
  isTestNumber: function(number){
    return CreditCard.TEST_NUMBERS.include(CreditCard.strip(number));
  },
  strip: function(number) {
    return number.gsub(/\s/,'');
  },
  type: function(number) {
    for(var card in CreditCard.CARDS)
      if(CreditCard['is'+card](number)) return card;
  }
};

(function(){
  for(var card in CreditCard.CARDS)
    CreditCard['is'+card] = function(card, number){
      return CreditCard.CARDS[card].test(CreditCard.strip(number));
    }.curry(card);
})();