Classes

Classes

TypeScript classes are JavaScript classes with type annotations. Declare property types in the class body:

class Animal {
    name: string;
    sound: string;

    constructor(name: string, sound: string) {
        this.name = name;
        this.sound = sound;
    }

    speak(): string {
        return this.name + " says " + this.sound;
    }
}

const dog = new Animal("Dog", "woof");
console.log(dog.speak());  // Dog says woof

Access Modifiers

TypeScript adds access modifiers:

• public — accessible anywhere (default)
• private — accessible only within the class
• readonly — can only be assigned once (in the constructor)

class Counter {
    private count: number = 0;

    increment(): void {
        this.count++;
    }

    value(): number {
        return this.count;
    }
}

Constructor Shorthand

TypeScript lets you declare and assign in one step:

class Point {
    constructor(public x: number, public y: number) {}

    toString(): string {
        return "(" + this.x + ", " + this.y + ")";
    }
}

Your Task

Write a class Circle with a radius: number property, a constructor, an area() method returning Math.PI * r * r rounded to 2 decimal places, and a perimeter() method returning 2 * Math.PI * r rounded to 2 decimal places.