// 父类
class Animal {
    constructor(name) {
        this.name = name;
    }
    speak() {
        return "some animal sound";
    }
}

// 子类
class Dog extends Animal {
    speak() {
        return this.name +":  Woof!";
    }
}

// 子类
class Cat extends Animal {
    speak() {
        return this.name +":  Meow!";
    }
}

// 使用
let dog = new Dog("阿狗");
let cat = new Cat("阿猫");

console.log(dog.speak()); // 输出: Woof!
console.log(cat.speak()); // 输出: Meow!