inheritance.js

/*
 * Task
 * We provide the implementation for a Rectangle class in the editor. Perform the following tasks:
 * Add an area method to Rectangle's prototype.
 * Create a Square class that satisfies the following:
 * It is a subclass of Rectangle.
 * It contains a constructor and no other methods.
 * It can use the Rectangle class' area method to print the area of a Square object.
 */

class Rectangle {
  constructor(w, h) {
    this.w = w;
    this.h = h;
  }
}

/*
*  Write code that adds an 'area' method to the Rectangle class' prototype
*/
Rectangle.prototype.area = function() { //NOTE: this not work with fatarrow... why?
  return (this.w * this.h); // Arrow functions provide a lexical this. this is a new this, not the this declared in the class
}
/*
* Create a Square class that inherits from Rectangle and implement its class constructor
*/
class Square extends Rectangle {
  constructor (length) {
    super(length, length);
  }
}

const rec = new Rectangle(3, 4);
const sqr = new Square(3);

console.log(rec.area());
console.log(sqr.area());