How do Classes work in TypeScript?

class User {
  name: string;
  age: number;

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

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

const user = new User("John", 30);

class BankAccount {
  public owner: string;      // accessible everywhere
  private balance: number;   // only in this class
  protected id: string;      // this class and subclasses

  constructor(owner: string, balance: number) {
    this.owner = owner;
    this.balance = balance;
    this.id = crypto.randomUUID();
  }
}

class User {
  constructor(
    public name: string,
    private age: number,
    readonly id: string
  ) {}
}
// Automatically creates and assigns properties

abstract class Shape {
  abstract getArea(): number;

  describe(): string {
    return `Area: ${this.getArea()}`;
  }
}

class Circle extends Shape {
  constructor(private radius: number) {
    super();
  }

  getArea(): number {
    return Math.PI * this.radius ** 2;
  }
}