TypeScript Builder Pattern Example

🎓 Top 15 Udemy Courses (80-90% Discount): My Udemy Courses - Ramesh Fadatare — All my Udemy courses are real-time and project oriented courses.

▶️ Subscribe to My YouTube Channel (178K+ subscribers): Java Guides on YouTube

▶️ For AI, ChatGPT, Web, Tech, and Generative AI, subscribe to another channel: Ramesh Fadatare on YouTube

This post shows how to use the Builder Pattern in TypeScript with an example.

The definition of the Builder Pattern is a separation of the construction of a complex object from its representation.

Problem Statement

Let's look at below code, there are many parameters in the constructor and it's a complex object.

export class House {
    address: string;
    floorNumber: number;
    city: string;
    isHavingParking: boolean;
    isHavingGarden: boolean;

    constructor(address: string, floorNumber: number, city: string, isHavingParking: boolean, isHavingGarden: boolean){
        this.address = address;
        this.floorNumber = floorNumber;
        this.city = city;
        this.isHavingParking = isHavingParking;
        this.isHavingGarden = isHavingGarden;
    }
}

function clientCode() {
    const myHouse = new House("Ramesh Fadatare 4803111", 14, "Pune", true, true);    
}

clientCode();

Let's solve the above problem using a builder pattern.

TypeScript Builder Pattern

Let's use Builder Pattern, the parameters in the constructor are reduced and served in a much more readable way, and thus there is no need to pass in null for optional parameters to the constructor.

Let’s create “builder.ts” file which contains the following code:

/**
 * The definition of the Builder Pattern is a separation of the 
 * construction of a complex object from its representation.
 * 
 */
export class House {
    address: string;
    floorNumber: number;
    city: string;
    isHavingParking: boolean;
    isHavingGarden: boolean;
    
    constructor(houseBuilder: HouseBuilder) {
        this.address = houseBuilder.address;
        this.city = houseBuilder.city;
        this.floorNumber = houseBuilder.floorNumber;
        this.isHavingParking = houseBuilder.isHavingParking;
        this.isHavingGarden = houseBuilder.isHavingGarden;
    }
}

/**
 * HouseBuilder implementation
 */
export class HouseBuilder {

    private readonly _address: string;
    private _floorNumber: number = 0;
    private _isHavingParking: boolean = false;
    private _city: string;
    private _isHavingGarden: boolean = false;

    constructor(address: string) {
        this._address = address;
    }

    setFloor(floor: number) {
        this._floorNumber = floor;
        return this;
    }

    setCity(city: string){
        this._city = city;
        return this;
    }

    makeParking() {
        this._isHavingParking = true;
        return this;
    }

    makeGarden() {
        this._isHavingGarden = true;
        return this;
    }

    build() {
        return new House(this);
    }

    get isHavingParking() {
        return this._isHavingParking;
    }

    get isHavingGarden() {
        return this._isHavingGarden;
    }

    get address() {
        return this._address;
    }

    get floorNumber() {
        return this._floorNumber;
    }

    get city(){
        return this._city;
    }
}

function clientCode() {
    const myHouse = new HouseBuilder('Ramesh Fadatare, Street: Katraj')
    .setCity("Pune")
    .setFloor(5)
    .makeGarden()
    .makeParking()
    .build();

    console.log(myHouse);
}

clientCode();

Notice that we always return this in every function (expect build). Well, this because we want to “chain” everything together, and then build and return the new house instance according to the builder state.

Run:

1. Compile the above code using the TypeScript compiler.
2. Above code is compiled to plan JavaScript code
3. Run Javascript code using node

C:\typescript-design-patterns\builder> tsc .\builder.ts
C:\typescript-design-patterns\builder> node .\builder.js

Output:

House {
  address: 'Ramesh Fadatare, Street: Katraj',
  city: 'Pune',
  floorNumber: 5,
  isHavingParking: true,
  isHavingGarden: true }

My Top and Bestseller Udemy Courses. The sale is going on with a 70 - 80% discount. The discount coupon has been added to each course below:

Build REST APIs with Spring Boot 4, Spring Security 7, and JWT

🆕 High-Demand 80–90% OFF

[NEW] Learn Apache Maven with IntelliJ IDEA and Java 25

🆕 High-Demand 80–90% OFF

ChatGPT + Generative AI + Prompt Engineering for Beginners

🚀 Trending Now 80–90% OFF

Spring 7 and Spring Boot 4 for Beginners (Includes 8 Projects)

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Building Real-Time REST APIs with Spring Boot - Blog App

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Building Microservices with Spring Boot and Spring Cloud

🌟 Top Rated 80–90% OFF
Available in Udemy for Business

Java Full-Stack Developer Course with Spring Boot and React JS

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Build 5 Spring Boot Projects with Java: Line-by-Line Coding

🌟 Top Rated 80–90% OFF

Testing Spring Boot Application with JUnit and Mockito

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Spring Boot Thymeleaf Real-Time Web Application - Blog App

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Master Spring Data JPA with Hibernate

🔥 Bestseller 80–90% OFF
Available in Udemy for Business

Spring Boot + Apache Kafka Course - The Practical Guide

🎓 Student Favorite 80–90% OFF
Available in Udemy for Business

Java Testing: Mastering JUnit 5 Framework

🆕 New 80–90% OFF

Reactive Programming in Java: Spring WebFlux and Testing

🌟 Top Rated 80–90% OFF

Spring Boot + RabbitMQ Course - The Practical Guide

🌟 Top Rated 80–90% OFF
Available in Udemy for Business

Functional Programming in Java (Includes Java Collections)

🎓 Student Favorite 80–90% OFF

ChatGPT for Java Developers: Boost Your Productivity with AI

🚀 Trending Now 80–90% OFF