Which constructor correctly extends the Dog class with a Labrador class constructor?

Which constructor correctly extends the Dog class with a Labrador class constructor?

• A. constructor(name, size) { this.size = size; }
• B. constructor(name, size) { super(name); this.size = size; }
• C. constructor(size) { super(name); this.size = size; }
• D. constructor(name, size) { this.name = name; this.size = size; }

Answer: (B)

In object-oriented programming, when creating a subclass, it is common to call the constructor of the parent class to ensure that the constraints and initializations defined in the parent class are properly applied to the new instance of the subclass. In this case, the Labrador class is extending the Dog class. The correct choice establishes this relationship by correctly invoking the parent class's constructor using the `super()` method. The `super(name)` call is necessary to initialize the inherited properties defined in the Dog class with the appropriate value for `name`. Additionally, it also properly initializes the `size` property specific to the Labrador class by assigning the provided `size` parameter to `this.size`. When creating subclasses, failing to call the parent's constructor often leads to errors, as critical initializations may be missing. The other options do not appropriately inherit from the Dog class’s constructor, either by omitting the `super` call, not matching the expected parameters for the Dog class, or incorrectly trying to initialize properties without referencing the parent class's constructor. Hence, option B is the right choice as it correctly utilizes inheritance in JavaScript through classes.

In object-oriented programming, when creating a subclass, it is common to call the constructor of the parent class to ensure that the constraints and initializations defined in the parent class are properly applied to the new instance of the subclass. In this case, the Labrador class is extending the Dog class.

The correct choice establishes this relationship by correctly invoking the parent class's constructor using the super() method. The super(name) call is necessary to initialize the inherited properties defined in the Dog class with the appropriate value for name. Additionally, it also properly initializes the size property specific to the Labrador class by assigning the provided size parameter to this.size.

When creating subclasses, failing to call the parent's constructor often leads to errors, as critical initializations may be missing. The other options do not appropriately inherit from the Dog class’s constructor, either by omitting the super call, not matching the expected parameters for the Dog class, or incorrectly trying to initialize properties without referencing the parent class's constructor. Hence, option B is the right choice as it correctly utilizes inheritance in JavaScript through classes.