JavaScript Objects and Prototypes Quiz

Review

1. What does Object.getPrototypeOf(object) return?

   It returns the object’s prototype link.
2. Which test checks only own-property membership?

   Object.hasOwn checks whether the property is directly present on the object.
3. If x exists only on a prototype, what does "x" in object return?

   The in operator includes inherited properties.
4. When object.x is assigned and x is only inherited as a data property, what normally happens?

   Ordinary assignment writes to the receiver in this case.
5. Why can one prototype method work for many instances?

   The same function can be called with different receivers.
6. What is the relationship between User.prototype and Object.getPrototypeOf(new User()) in the usual constructor case?

   new normally creates the instance with User.prototype as its prototype.
7. Where does a normal class instance method live?

   Class instance methods are placed on the class prototype.
8. What does Object.create(null) provide?

   The resulting object has no prototype.
9. Which data-property descriptor controls assignment?

   writable controls whether the data value may be changed by assignment.
10. What does a prototype link mean?

    A prototype is a delegation link used during object operations such as property lookup.