22.Class继承

 class Animal {
      constructor(name) {
        this.name = name;
      }
      getName() {
        return this.name;
      }
    }
    class Dog extends Animal {
      constructor(name, age) {
        super(name);
        this.type = "animal";
        this.age = age;
      }
    }
    class Cat {
      constructor(age) {
        this.age = age;
      }
    }
    let dog = new Dog();
    dog.name = "中华田园犬";
    dog.age = 5;
    let cat = new Cat();
    cat.age = 4;
    cat.name = "布偶猫";
    console.log(333, dog,cat);//{name:'中华田园犬',age:5,type:'animal'}  {name:'布偶猫',age:4}
    console.log(333,dog.getName());//中华田园犬
    console.log(333,cat.getName());//报错 cat.getName is not a function