I can have a getter in a JavaScript object like this:

var member = {

    firstName:"XYZ", 

    lastName:"zzz", 

    get fullName(){ return (this.firstName + ' ' + this.lastName); }

}

I can even add more properties on the fly, like this:

member.isGuest = true;

But, is there any way we can add getters to an existing object? Something like this:

member.isGuest = get isGuest(){ return this.firstName == 'Guest'; }