field validation and formatting pattern for credit card?

Hi Scott.

I am in the process of updating Private Number and will be sure to include some documentation about credit card regex in the next releae. There can be quite a bit of logic behind credit card validation, so there will likely not be a one-size-fits-all regex solution. For example, here is some code I dug up from a prior ecommerce project:

   if (type == "Visa") {
      // Visa: length 16, prefix 4, dashes optional.
      var re = /^4\d{3}-?\d{4}-?\d{4}-?\d{4}$/;
   } else if (type == "MC") {
      // Mastercard: length 16, prefix 51-55, dashes optional.
      var re = /^5[1-5]\d{2}-?\d{4}-?\d{4}-?\d{4}$/;
   } else if (type == "AmEx") {
      // American Express: length 15, prefix 34 or 37.
      var re = /^3[4,7]\d{13}$/;
   } else if (type == "Disc") {
      // Discover: length 16, prefix 6011, dashes optional.
      var re = /^6011-?\d{4}-?\d{4}-?\d{4}$/;
   } else if (type == "Diners") {
      // Diners: length 14, prefix 30, 36, or 38.
      var re = /^3[0,6,8]\d{12}$/;
   }

I found the following regex for Amex, Visa and Mastercard (not Discover or Diners) which does not capture the nuances of the above code, but might work as a first pass. I have yet to test it:

((4\d{3})|(5[1-5]\d{2}))\-(\d{4}\-){3}|^(3[4,7]\d{2})\-\d{6}\-\d{5}

http://www.regular-expressions.info/creditcard.html

This pattern work for me:

For Visa, MasterCard :
((4\d{3})|(5[1-5]\d{2}))( |)?\d{4}(\4\d{4}){2}

For Visa, MasterCard, Discover:
((4\d{3})|(5[1-5]\d{2})|(6011))( |)?\d{4}(\5\d{4}){2}

based on: http://www.explainth.at/en/re/repats.shtml

cheers!