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.

rectangle = new Rectangle(2, 5);

square = new Square(4, 4);


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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.

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);


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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.

Завдання

Swipe to start coding

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.

Рішення

class Rectangle {

height;

width;

constructor(height, width) {

this.height = height;

this.width = width;

console.log('Rectangle created');

}

class Square extends Rectangle{

color;

constructor(size, color){

super(size, size);

this.color = color;

console.log('Square created');

}

square = new Square(5, 'green');

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Секція 4. Розділ 2

class Rectangle {

height;

width;

constructor(height, width) {

this.height = height;

this.width = width;

console.log('Rectangle created');

}

class Square extends Rectangle{

// place your code here

}

square = new Square(12, 'green');