FAQ: Classes - Review: Classes


This community-built FAQ covers the “Review: Classes” exercise from the lesson “Classes”.

Paths and Courses
This exercise can be found in the following Codecademy content:

Web Development

Introduction To JavaScript

FAQs on the exercise Review: Classes

There are currently no frequently asked questions associated with this exercise – that’s where you come in! You can contribute to this section by offering your own questions, answers, or clarifications on this exercise. Ask or answer a question by clicking reply (reply) below.

If you’ve had an “aha” moment about the concepts, formatting, syntax, or anything else with this exercise, consider sharing those insights! Teaching others and answering their questions is one of the best ways to learn and stay sharp.

Join the Discussion. Help a fellow learner on their journey.

Ask or answer a question about this exercise by clicking reply (reply) below!

Agree with a comment or answer? Like (like) to up-vote the contribution!

Need broader help or resources? Head here.

Looking for motivation to keep learning? Join our wider discussions.

Learn more about how to use this guide.

Found a bug? Report it!

Have a question about your account or billing? Reach out to our customer support team!

None of the above? Find out where to ask other questions here!


Hey all, my question relates to the following code, where I’ve attempted to create a new Doctor class under the HospitalEmployee super class. Everything seems to work ok, however I also added an ‘addInsurance’ method which returns an error when invoked ‘is not a function at doctor.addInsurance’ . Does anyone know why this is the case?
class Doctor extends HospitalEmployee {
constructor(name, insurance) {
this._insurance = insurance;
get insurance() {
return this._insurance;


It looks like this._insurance is a singular value, not an array. We cannot push to a non-array object.


Oh that makes perfect sense now! Thanks Roy