Test for major credit card types

payment.js

function detect_card_type(card_number) {
        if (!_.isString(card_number) || _.isEmpty(card_number.trim())) {
            return null;
        }
        c = card_number.trim();

        // http://en.wikipedia.org/wiki/List_of_Issuer_Identification_Numbers
        if (/^[1-2]/.test(c)) return 'airline';
        if (/^3[06]/.test(c)) return 'diners';
        if (/^3[47]/.test(c)) return 'amex';
        if (/^35/.test(c)) return 'jcb';
        if (/^4/.test(c)) return 'visa';
        if (/^5[1-5]/.test(c)) return 'mastercard';
        return 'other';
    }