README.md

Factory Method Pattern

The Factory Method pattern lets a class defer instantiation to subclasses. It defines an interface for creating a single object, but lets subclasses decide which class to instantiate.

Example

// Class for Car
class Car {
  constructor({ doors = 4, state = "brand new", color = "silver" } = {}) {
    this.doors = doors;
    this.state = state;
    this.color = color;
  }
}

The Car class initializes a car object with properties doors, state, and color. Default values are provided using destructuring and default parameters.

// Class for Truck
class Truck {
  constructor({ doors = 2, state = "used", color = "blue" } = {}) {
    this.doors = doors;
    this.state = state;
    this.color = color;
  }
}

Similar to the Car class, the Truck class initializes a truck object with properties doors, state, and color. Default values are also provided using destructuring and default parameters.

// Factory class
class VehicleFactory {
  // Method to create a vehicle based on the provided options
  createVehicle(options) {
    switch (options.vehicleType) {
      // If vehicleType is "car", create a new Car
      case "car":
        return new Car(options);
      // If vehicleType is "truck", create a new Truck
      case "truck":
        return new Truck(options);
      // If vehicleType is not recognized, return null
      default:
        return null;
    }
  }
}

Explaining the code

• The createVehicle method is added to the VehicleFactory class.
• It takes an options object as an argument and uses a switch statement to determine which type of vehicle to create based on the vehicleType property.
• If vehicleType is "car", it creates and returns a new Car object.
• If vehicleType is "truck", it creates and returns a new Truck object.
• If vehicleType is not recognized, it returns null.

Usage

const factory = new VehicleFactory();

// Create a car with specified options
const car = factory.createVehicle({
  vehicleType: "car",
  doors: 4,
  color: "red",
  state: "new",
});

// Create a truck with specified options
const truck = factory.createVehicle({
  vehicleType: "truck",
  doors: 2,
  color: "black",
  state: "used",
});

Summary

This pattern allows the instantiation logic to be deferred to subclasses, promoting flexibility and scalability in object creation.