README.md

Builder Pattern

The Builder pattern separates the construction of a complex object from its representation. This allows the same construction process to create different representations of the object.

Example

// The Car class represents a car with various properties such as make, model, year, color, and engine. It uses a builder object to initialize these properties.
class Car {
  constructor(builder) {
    this.make = builder.make;
    this.model = builder.model;
    this.year = builder.year;
    this.color = builder.color;
    this.engine = builder.engine;
  }

  // Returns a string representation of the car
  toString() {
    return `${this.year} ${this.make} ${this.model} in ${this.color} with a ${this.engine} engine`;
  }
}

The CarBuilder class helps in building a Car object step by step. It allows setting various properties of the car and then building the final Car object.

// CarBuilder class helps in building a Car object step by step
class CarBuilder {
  constructor(make, model) {
    this.make = make;
    this.model = model;
  }

  // Sets the year of the car
  setYear(year) {
    this.year = year;
    return this;
  }

  // Sets the color of the car
  setColor(color) {
    this.color = color;
    return this;
  }

  // Sets the engine type of the car
  setEngine(engine) {
    this.engine = engine;
    return this;
  }

  // Builds and returns a Car object
  build() {
    return new Car(this);
  }
}

Explaining the code

1. Fluent Interface: The CarBuilder class uses a fluent interface, allowing method chaining. Each setter method returns the builder object itself (this), enabling chaining multiple method calls in a single statement.
2. Separation of Concerns: The builder pattern separates the construction of a complex object (Car) from its representation, allowing the same construction process to create various representations.
3. Immutability: Once a Car object is created, its properties are immutable (cannot be changed), ensuring the integrity of the object.

Usage

const car = new CarBuilder("Toyota", "Camry")
  .setYear(2021)
  .setColor("Red")
  .setEngine("V6")
  .build();

// Output the car details
console.log(car.toString());

Summary

In this example, the Product class is constructed using the Builder class. The Builder class provides methods to set optional parameters and a build() method to create the Project object. The Builder pattern is useful for constructing complex objects with many optional parameters.