ES6 class inheritance

JavaScript

class Rectangle extends Again {
	constructor(length, width) {
  	this.length = length;
    this.width = width;
  }
  
  getArea() {
  	return this.length * this.width;
  }
}

class Square extends Rectangle {
	constructor(length) {
  	super(length, length);
  }
}

class Again extends Square {
	constructor(length) {
  	super(length, length);
  }
}

var square = new Again(3);

console.log(square.getArea());
console.log(square instanceof Square);
console.log(square instanceof Rectangle);