Class, Constructor, Factory

class-constructor-factory-examples.js

// class
class ClassCar {
  drive () {
    console.log('Vroom!');
  }
}

const car1 = new ClassCar();
car1.drive();


// constructor
function ConstructorCar () {}

ConstructorCar.prototype.drive = function () {
  console.log('Vroom!');
};

const car2 = new ConstructorCar();
car2.drive();


// factory
const proto = {
  drive () {
    console.log('Vroom!');
  }
};

const factoryCar = () => Object.create(proto);

const car3 = factoryCar();
car3.drive();

But when to use what ?

I don't use any of these in real applications most of the time. Instead, I use factory functions without prototype links most of the time:

const noProtoCar = () => ({
  drive: () => console.log('Vroom!')
});

const car = noProtoCar();
car.drive(); // "Vroom!"

However, I use those mostly for plain data objects, instead of behavior, and then define behaviors separately:

const createVehicle = ({wheels}) => ({
  sound = 'Vroom!',
} = {}) => ({
  sound,
  wheels,
});

const createCar = createVehicle({ wheels: 4 });

// Define behaviors as separate functions - makes them more reusable across many different types of objects.
const drive = ({ sound }) => console.log(sound);

const car = createCar();
drive(car); // Vroom!

// Now we can use it with motorcycles too!
const createMotorcycle = createVehicle({ wheels: 2 });

const motorcycle = createMotorcycle({ sound: 'Brrrrrrrrrrrrm!' });
drive(motorcycle); // Brrrrrrrrrrrrm!

This style is called functional programming. I wrote a whole book about it.