Thank you Ninja but what do the dbField represent? Is it member ID (_id) or is it the field for expiration date of a rented video? 
It may be a stupid question but I wanna know if you already in the beginning of the code are combining the check of current member with checking if the expirydate-field is empty or not?
Another question; I prefer to use nickname instead of firstName and lastName so why can I not write in this way instead? (ānicknameā become redmarked). <ā hm?
const nickname = ${ member . contactDetails .nickname};