Classes & Inheritance Drills

Use classes to bundle state with behaviour. Constructors, methods, static, getters, inheritance, and private fields with #.

Step 1 of 7

Why classes exist

You can model anything with plain objects and functions — but once a thing has both state and behaviour tied together, classes give you a clean shape for them.

Real-world examples you have already used:

Every built-in Error in the browser is a class. TypeError, RangeError, and your own custom errors all extend Error.
The DOM’s EventTarget, HTMLElement, and HTMLInputElement are a class hierarchy.
Three.js scenes, React class components, and most game engines are class-heavy.

This lesson is a tour of the syntax in the order you’ll need it: declaration, methods, static, getters/setters, extends/super, and private fields with #.

Think of it this way: A class is a blueprint. The constructor is the assembly line — given some parts (the arguments), it builds an instance with state and methods baked in.

Learn more on MDN

Classes (MDN)