src/builder/index.ts

// https://en.wikipedia.org/wiki/Factory_method_pattern

namespace BuilderPattern {
  /*-------------Classic-------------*/

  class Product {
    public parts: string[] = [];

    public listParts(): void {
      console.log(`Product parts: ${this.parts.join(", ")}\n`);
    }
  }

  interface Builder {
    producePartA(): void;
    producePartB(): void;
    producePartC(): void;

    createNewProduct(): void;
    get product(): Product;
  }

  class ConcreteBuilder implements Builder {
    private _product: Product;
    public get product(): Product {
      return this._product;
    }

    constructor() {
      this.newProduct();
    }

    createNewProduct(): void {
      this.newProduct();
    }

    public producePartA(): void {
      this._product.parts.push("PartA");
    }

    public producePartB(): void {
      this._product.parts.push("PartB");
    }

    public producePartC(): void {
      this._product.parts.push("PartC");
    }

    private newProduct() {
      this._product = new Product();
    }
  }

  class Director {
    private builder: Builder;

    public setBuilder(builder: Builder): void {
      this.builder = builder;
    }

    public buildMinimalViableProduct(): void {
      this.builder.createNewProduct();
      this.builder.producePartA();
    }

    public buildFullFeaturedProduct(): void {
      this.builder.createNewProduct();
      this.builder.producePartA();
      this.builder.producePartB();
      this.builder.producePartC();
    }
  }

  // Client code

  const director = new Director();
  const builder = new ConcreteBuilder();
  director.setBuilder(builder);

  console.log("Standard basic product:");
  director.buildMinimalViableProduct();
  builder.product.listParts();

  console.log("Standard full featured product:");
  director.buildFullFeaturedProduct();
  builder.product.listParts();

  // Output

  /*
  Standard basic product:
  Product parts: PartA

  Standard full featured product:
  Product parts: PartA, PartB, PartC
  */

  /*-------------New way-------------*/

  class User {
    private name: string;
    private age: number;
    private phone: string;
    private address: string;

    constructor(builder: UserBuilder) {
      this.name = builder.Name;
      this.age = builder.Age;
      this.phone = builder.Phone;
      this.address = builder.Address;
    }

    get Name() {
      return this.name;
    }
    get Age() {
      return this.age;
    }
    get Phone() {
      return this.phone;
    }
    get Address() {
      return this.address;
    }
  }

  class UserBuilder {
    private name: string;
    private age: number;
    private phone: string;
    private address: string;

    constructor(name: string) {
      this.name = name;
    }

    get Name() {
      return this.name;
    }
    setAge(value: number): UserBuilder {
      this.age = value;
      return this;
    }
    get Age() {
      return this.age;
    }
    setPhone(value: string): UserBuilder {
      this.phone = value;
      return this;
    }
    get Phone() {
      return this.phone;
    }
    setAddress(value: string): UserBuilder {
      this.address = value;
      return this;
    }
    get Address() {
      return this.address;
    }

    build(): User {
      return new User(this);
    }
  }

  // Client code

  const u = new UserBuilder("catchzeng")
    .setAge(30)
    .setPhone("0123456789")
    .setAddress("asdf")
    .build();
  console.log(u.Name + " " + u.Age + " " + u.Phone + " " + u.Address);

  // Output

  /*
  catchzeng 30 0123456789 asdf
  */
}