A polymorphism example with classes in Typescript

polymorphism.ts

export abstract class Vehicle {
  public abstract wheels: number;

  public get name() {
    return this.constructor.name;
  }
}

export class Bicycle extends Vehicle {
  public get wheels() {
    return 2;
  }
}

export class Car extends Vehicle {
  public get wheels() {
    return 4;
  }
}

export class Truck extends Vehicle {
  public get wheels() {
    return 18;
  }
}

export class VehicleList {
  private readonly vehicles: Vehicle[];

  public static empty() {
    return new VehicleList([]);
  }

  public add(vehicle: Vehicle) {
    this.vehicles.push(vehicle);

    return this;
  }

  public print() {
    this.vehicles.forEach((vehicle) => {
      console.log(`A ${vehicle.name} has ${vehicle.wheels} wheels.`);
    });
  }

  private constructor(vehicles: Vehicle[]) {
    this.vehicles = vehicles;
  }
}

function main() {
  VehicleList.empty()
    .add(new Bicycle())
    .add(new Car())
    .add(new Truck())
    .print();
}

main();