If you wish to represent a gift card to the server as a payment type, you utilize ECECardPayment. If the idea sounds familiar, it may be because Nintendo used them - ECards are officially Wii Points Cards.
For example, assuming every ECard is 16 digits long:
var payment =newECECardPayment('001122334455667788');
The typically 16 digit card number set during instantiation. Can be retrieved, or set to another set of digits.