exercise for https://people.mozilla.org/~mconley2/talks/js-and-dom-for-gecko-hackers-talk/#slide-52

mozquiz.js

function Shape({ x, y }) {
  this._x = x;
  this._y = y;
}

Shape.prototype = {
  get coords() {
    return { x: this._x, y: this._y };
  },
}

function Rect({x, y, h, w}) {
  Shape.call(this, {x, y});
  this._h = h;
  this._w = w;
}

Rect.prototype = Object.create(Shape.prototype);
Object.defineProperty(Rect.prototype, 'isSquare', {
  get: function() {
    return this._x === this._y && this._x === this._h && this._x === this._w;
  }
});

// Implement Rect, which subclasses Shape. In addition to
// the x and y coordinate parameters, should also take height
// and width. Should also have a isSquare getter that returns
// true if the Rect is square.

let s = new Rect({ x: 15, y: 25, h: 5, w: 5 });
console.log(s.isSquare);

let rects = [
  new Rect({ x: 0, y: 0, h: 5, w: 100 }),
  new Rect({ x: 0, y: 5, h: 13, w: 2 }),
  new Rect({ x: 10, y: 10, h: 15, w: 15 }),
  new Rect({ x: 16, y: -5, h: 3, w: 3 }),
];

// Iterate the rects using for...of, and console.log
// isSquare for each.

for (let x of rects) {
  console.log(x.isSquare);
}

/*
// Using object destructuring to assign the coords of
// s to local variables x and y in a single line.
*/
let {x, y} = s.coords;
console.log(x, y);