Constructor Inheritance

If there is a constructor in the parent class, the daughter class will inherit it. Here you create square, but use a Rectangle constructor, so you should pass both height and width parameters.


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rectangle = new Rectangle(2, 5);
square = new Square(4, 4);

This is a bit inconvenient, so let's create constructor for Square class, that will use Rectangle constructor. To do that in daughter class, you should use super() function to call the parent constructor first.


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class Rectangle {
  height;
  width;
  constructor(height, width) {
    this.height = height;
    this.width = width;
    console.log('Rectangle created');
  }
}

class Square extends Rectangle{
  constructor(size){
    super(size, size);
    // init other attributes if it is required
    console.log('Square created');
  }
}

square = new Square(5);

This way, first you call Rectangle's constructor(height, width), and after define other attributes initialization. Then Square`s constructor is called. This way, first you create parent's object, and after that daughter's one.

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To the class Square, add attribute color. Then create constructor with two parameters: side length and color. In its body, call Rectangle constructor to initialize width and length, and then initialize color.

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Sektion 4. Kapitel 2

Constructor Inheritance

If there is a constructor in the parent class, the daughter class will inherit it. Here you create square, but use a Rectangle constructor, so you should pass both height and width parameters.


              12
            
rectangle = new Rectangle(2, 5);
square = new Square(4, 4);


              12345678910111213141516171819
            
class Rectangle {
  height;
  width;
  constructor(height, width) {
    this.height = height;
    this.width = width;
    console.log('Rectangle created');
  }
}

class Square extends Rectangle{
  constructor(size){
    super(size, size);
    // init other attributes if it is required
    console.log('Square created');
  }
}

square = new Square(5);

Opgave

Swipe to start coding

Løsning

Skift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder

Var alt klart?

Tak for dine kommentarer!

Sektion 4. Kapitel 2

Skift til skrivebord for at øve i den virkelige verdenFortsæt der, hvor du er, med en af nedenstående muligheder