访问ES6超级属性

所以当我看到令人惊讶的事情时,我正在搞乱ES6课程:

class Animal {
    constructor(name) {
        this.name = name;
    }
    speak(sound) {
        console.log(sound);
    }
}

class Dog extends Animal {
    constructor(name, age) {
        super(name);
        this.age = age;
    }
    speak() {
        super.speak("Woof! I'm " + super.name + " and am " + this.age);
    }
}

然后,我创造了我的狗:

var mydog = new Dog("mydog",3);
mydog.speak();

现在这个打印

Woof! I'm undefined and am 3

super.speak("Woof! I'm " + this.name + " and am " + this.age);