// 抽象类不能创建实例
(function () {
  abstract class Animal {
    name: string;
    constructor(name: string) {
      this.name = name;
    }
    // 抽象方法只能且必须在子类进行重写
    abstract sayHi(): void;
  }

  class Dog extends Animal {
    sayHi() {
      console.log("hihihi");
    }
  }
  class Cat extends Animal {
    constructor(name: string) {
      super(name);
    }
    sayHi() {
      console.log("hi");
    }
  }
})();