superキーワードの使い方 | 継承とサブクラス | JavaScript 超完全入門 基本から発展までのすべて

class Animal {
    constructor(name) {
        this.name = name;
    }

    speak() {
        console.log(this.name + " makes a noise.");
    }
}

class Dog extends Animal {
    constructor(name, breed) {
        super(name);  // 親クラスのコンストラクタを呼び出す
        this.breed = breed;
    }

    speak() {
        console.log(this.name + " barks.");
    }
}

const dog = new Dog("Rex", "Labrador");
dog.speak();  // "Rex barks."
console.log(dog.breed);  // "Labrador"

class Animal {
    constructor(name) {
        this.name = name;
    }

    speak() {
        console.log(this.name + " makes a noise.");
    }
}

class Dog extends Animal {
    speak() {
        super.speak();  // 親クラスのspeakメソッドを呼び出す
        console.log(this.name + " barks.");
    }
}

const dog = new Dog("Rex");
dog.speak();  
// "Rex makes a noise."
// "Rex barks."

class Vehicle {
    constructor(brand) {
        this.brand = brand;
    }

    startEngine() {
        console.log(this.brand + " engine started.");
    }
}

class Car extends Vehicle {
    startEngine() {
        super.startEngine();  // 親クラスのstartEngineを呼び出し
        console.log(this.brand + " is ready to go!");
    }
}

const car = new Car("Toyota");
car.startEngine();  
// "Toyota engine started."
// "Toyota is ready to go!"

class Animal {
    constructor(name) {
        this.name = name;
    }
}

class Cat extends Animal {
    introduce() {
        console.log("My name is " + this.name);
    }
}

const cat = new Cat("Whiskers");
cat.introduce();  // "My name is Whiskers"

class Animal {
    constructor(name) {
        this.name = name;
    }
}

class Dog extends Animal {
    constructor(name, breed) {
        // thisを使う前にsuperを呼び出す必要がある
        super(name);
        this.breed = breed;
    }
}

const dog = new Dog("Rex", "Labrador");
console.log(dog.name);  // "Rex"
console.log(dog.breed);  // "Labrador"