Decorator pattern

abstract class Beverage {
  description: string = "Unknown beverage";

  getDescription() {
    return this.description;
  }

  cost(): number {
    return 0;
  }
}

class CondimentDecorator extends Beverage {
  getDescription() {}
}

class DarkRoast extends Beverage {
  description = "Dark roast coffee";

  cost(): number {
    return 0.99;
  }
}

class Espresso extends Beverage {
  description = "Espresso";

  cost(): number {
    return 1.99;
  }
}

class HouseBlend extends Beverage {
  description = "House Blend Coffee";

  cost(): number {
    return 0.89;
  }
}

class Decaf extends Beverage {
  description = "Decaffeinated coffee";

  cost(): number {
    return 1.05;
  }
}

class Milk extends CondimentDecorator {
  beverage: Beverage;

  constructor(beverage: Beverage) {
    super();
    this.beverage = beverage;
  }

  getDescription() {
    return this.beverage.getDescription() + ", Milk";
  }

  cost(): number {
    return 0.1 + this.beverage.cost();
  }
}

class Mocha extends CondimentDecorator {
  beverage: Beverage;

  constructor(beverage: Beverage) {
    super();
    this.beverage = beverage;
  }

  getDescription() {
    return this.beverage.getDescription() + ", Mocha";
  }

  cost(): number {
    return 0.2 + this.beverage.cost();
  }
}

class Soy extends CondimentDecorator {
  beverage: Beverage;

  constructor(beverage: Beverage) {
    super();
    this.beverage = beverage;
  }

  getDescription() {
    return this.beverage.getDescription() + ", Soy";
  }

  cost(): number {
    return 0.1 + this.beverage.cost();
  }
}

class Whip extends CondimentDecorator {
  beverage: Beverage;

  constructor(beverage: Beverage) {
    super();
    this.beverage = beverage;
  }

  getDescription() {
    return this.beverage.getDescription() + ", Whip";
  }

  cost(): number {
    return 0.1 + this.beverage.cost();
  }
}

let myOrder = new DarkRoast();
myOrder = new Milk(myOrder);
myOrder = new Mocha(new Mocha(myOrder));
myOrder = new Whip(myOrder);

console.log(myOrder.getDescription());
console.log(myOrder.cost());