Session
    
    onEmptinessChange
onEmptinessChange Callback
The onEmptinessChange( ) callback method is invoked when the hosted field becomes empty or is no longer empty.
Usage
PaymentSession.onEmptinessChange([HostedFieldsRole], function(selector, result), [scope])
Example
PaymentSession.onEmptinessChange(["card.number", "card.nameOnCard"], function(selector, result) {
    //handle change event
    if (result.isEmpty) {
        // field has empty value
        console.log("Element with selector " + selector + " has changed it's emptiness status to empty");
    } else if (!result.isEmpty) {
        // field has non-empty value
        console.log("Element with selector " + selector + " has changed it's emptiness status to non-empty");
    }
});
Arguments
        HostedFieldsRole
        
        Array
        REQUIRED
    
    An array of field roles for the hosted fields where the event occurred. Valid array of field roles:
card.nameOnCard
            card.number
            card.expiryMonth
            card.expiryYear
            card.securityCode
            giftCard.number
            giftCard.pin
            ach.bankAccountNumber
            ach.bankAccountHolder
            ach.routingNumber
            
        callbackFunction
        
        Function
        
    The callback function invoked when the event is triggered.
        scope
        
        String
        
    The optional named instance of a card payment data set within a session. See Multiple Hosted Sessions for more information.
Return Value
None