(function(){

class Animal{

  name:string;

  constructor(name:string){

    this.name=name;

  }

  sayHello(){

    console.log('动物再叫---');

  }

}

class Dog extends Animal {

  age:number;

  constructor(name:string,age:number){

    super(name);

    this.age=age;

  }

    sayHello() {

      // super.sayHello();

      console.log('汪汪汪！');

    }

}

const dog=new Dog('旺财',18);

dog.sayHello();

})();