Angular 2:如何在一个数组中返回属于扩展超类的多个类的对象？

class Animal {
  name: string;
  constructor(name: string) {
    this.name = name;
  }
}

class Cat extends Animal {
  breed: string;
  constructor(name: string, breed: string) {
    super(name);
    this.breed = breed;
  }
}

class Dog extends Animal {
  age: number;
  constructor(name: string, age: number) {
    super(name);
    this.age = age;
  }
}

let animals: Animal[] = [
  new Cat("Tom", "Persian"),
  new Dog("Max", 3),
  new Cat("Kitty", "Siamese"),
  new Dog("Buddy", 5)
];

let cats: Cat[] = animals.filter((animal) => animal instanceof Cat) as Cat[];

let dogs: Dog[] = animals.filter((animal) => animal instanceof Dog) as Dog[];