Try It Yourself - SyntaxStudy Editor

HTML / CSS / JS

// Parameter properties shorthand
class Person {
    constructor(
        public readonly id: number,
        public name: string,
        protected email: string,
        private _passwordHash: string,
    ) {}

greet(): string {
        return `Hi, I'm ${this.name}`;
    }
}

// Abstract base class
abstract class Shape {
    constructor(public readonly color: string) {}

abstract area(): number;      // must be implemented
    abstract perimeter(): number; // must be implemented

describe(): string {
        return `A ${this.color} shape with area ${this.area().toFixed(2)}`;
    }
}

class Circle extends Shape {
    constructor(color: string, public readonly radius: number) {
        super(color);
    }
    area():      number { return Math.PI * this.radius ** 2; }
    perimeter(): number { return 2 * Math.PI * this.radius;   }
}

class Rectangle extends Shape {
    constructor(
        color: string,
        public readonly width: number,
        public readonly height: number,
    ) { super(color); }
    area():      number { return this.width * this.height; }
    perimeter(): number { return 2 * (this.width + this.height); }
}

const c = new Circle("red", 5);
const r = new Rectangle("blue", 4, 6);
console.log(c.describe()); // A red shape with area 78.54
console.log(r.describe()); // A blue shape with area 24.00