Interfaces in TypeScript

interface Speaker {
    speak(): void;
}
class Dog implements Speaker {
    speak(): void { console.log("Woof"); }
}

Full lesson:

An interface defines what a class can do, not how it does it or what it is. A Truck, a Robot, and a Drone aren't the same kind of thing — but they can all move(). You'd put move() in a Movable interface and have each one implement it.

Interface vs abstract class

A class inherits from at most one parent class but can implement many interfaces. That's why interfaces are the right tool for cross-cutting capabilities like Comparable, Serializable, Iterable, etc.

Interfaces in TypeScript:

TypeScript has a real interface keyword. An interface describes the shape an object or class must have — the methods and properties it must provide — and a class then implements it.

interface Speaker {
    speak(): void;
}

class Dog implements Speaker {
    speak(): void { console.log("Woof"); }
}

The implements keyword makes the compiler check that Dog really provides every member Speaker requires — which is exactly what you'll do in the task below. Interfaces exist only at compile time: they are erased from the compiled JavaScript.

Your task

The Speaker interface is already declared. Create a Dog class that implements it, with a speak() method that prints "Woof".

Expected output:

Woof