Builder

Builder is a creational design pattern that lets you construct complex objects step by step.

The pattern allows you to produce different types and representations of an object using the same construction code.

The Builder design pattern is a creational pattern used to construct complex objects step by step.

It separates the construction of a complex object from its representation, allowing the same construction process to create different representations.

// Product
class Pizza {
  constructor() {
    this.size = '';
    this.crust = '';
    this.toppings = [];
  }

  describe() {
    console.log(`Size: ${this.size}, Crust: ${this.crust}, Toppings: ${this.toppings.join(', ')}`);
  }
}

// Builder
class PizzaBuilder {
  constructor(size) {
    this.pizza = new Pizza();
    this.pizza.size = size;
  }

  addCrust(crust) {
    this.pizza.crust = crust;
    return this;
  }

  addTopping(topping) {
    this.pizza.toppings.push(topping);
    return this;
  }

  build() {
    return this.pizza;
  }
}

// Usage
const pizza = new PizzaBuilder('Large')
  .addCrust('Thin')
  .addTopping('Mushrooms')
  .addTopping('Pepperoni')
  .build();

pizza.describe(); // Output: Size: Large, Crust: Thin, Toppings: Mushrooms, Pepperoni

In this example:

• Pizza is the product class representing the complex object we want to build.

• PizzaBuilder is the builder class that helps in constructing the Pizza object step by step.

• The builder class allows setting different attributes of the Pizza object and then finally builds the Pizza object with the build() method.

This pattern allows for flexibility in constructing complex objects, as you can add or change the construction process without affecting the client code.