function Vehicle(type) {
  this.type = type;
}

Vehicle.prototype.describe = function() {
  return `This is a ${this.type}`;
};

function Car(brand) {
  Vehicle.call(this, 'car');
  this.brand = brand;
}

Car.prototype = Object.create(Vehicle.prototype);
Car.prototype.constructor = Car;

Car.prototype.describe = function() {
  return Vehicle.prototype.describe.call(this) + ` made by ${this.brand}`;
};

const tesla = new Car('Tesla');
console.log(tesla.describe());
console.log(tesla.constructor.name);

const Maybe = {
  of: (value) => ({ value, map: f => value == null ? Maybe.nothing() : Maybe.of(f(value)) }),
  nothing: () => ({ value: null, map: () => Maybe.nothing() })
};

const result = Maybe.of(5)
  .map(x => x * 2)
  .map(x => x > 15 ? null : x)
  .map(x => x + 1)
  .map(x => x.toString());

console.log(result.value);