JuniorTheoryCommon

What does the program print?

JavaScript

class Animal {
    speak() {
        return "Hi";
    }
}
class Dog extends Animal {
    speak() {
        return super.speak() + " Woof";
    }
}
const d = new Dog();
console.log(d.speak());

Hi Woof

Expecting Hi: a method in Dog overrides the one in Animal, so d.speak() runs the Dog version, which adds " Woof" to the parent's result.
Expecting super.speak() to call the speak of Dog again: super looks in the parent class, so it runs the speak of Animal, which returns "Hi".

What does the program print if Dog returns "Woof" without calling super.speak()?
What does d instanceof Animal evaluate to, and why?

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JuniorTheoryCommon

What does the program print?

JavaScript

class Animal {
    speak() {
        return "Hi";
    }
}
class Dog extends Animal {
    speak() {
        return super.speak() + " Woof";
    }
}
const d = new Dog();
console.log(d.speak());

Hi Woof

Expecting Hi: a method in Dog overrides the one in Animal, so d.speak() runs the Dog version, which adds " Woof" to the parent's result.
Expecting super.speak() to call the speak of Dog again: super looks in the parent class, so it runs the speak of Animal, which returns "Hi".

What does the program print if Dog returns "Woof" without calling super.speak()?
What does d instanceof Animal evaluate to, and why?

Back to questions Open topic in roadmap →Answer it yourself — Quiz