In this article, we will learn how to use and implement the Factory Design Pattern in TypeScript with an example.

The factory design pattern overview

Factory Pattern is one of the Creational Design Pattern.
In the Factory pattern, we create an object without exposing the creation logic to the client and refer to newly created objects using a common interface.
The factory design pattern is used when we have a superclass with multiple sub-classes and based on input, we need to return one of the sub-class. This pattern takes out the responsibility of the instantiation of a class from the client program to the factory class.

TypeScript Factory Design Pattern Example

Let's create factory_method.ts file and add the following code to it:

export interface Product {
    method(param?: any) : void;
}

export class ConcreteProductA implements Product {
    method = (param?: any) => {
        return "Method of ConcreteProductA";
    }
}

export class ConcreteProductB implements Product {
    method = (param?: any) => {
        return "Method of ConcreteProductB";
    }
}


export class ProductFactory {
    public static createProduct(type: string) : Product {
        if (type === "A") {
            return new ConcreteProductA();
        } else if (type === "B") {
            return new ConcreteProductB();
        }

        return null;
    }
}

Usage

Let's create demo.ts file and add the following code to it:

import { Product, ProductFactory } from "./factoryMethod";

export function show() : void {
 var a: Product = ProductFactory.createProduct("A");
 var b: Product = ProductFactory.createProduct("B");

 console.log(a.method());
 console.log(b.method());
};

show();

Run:

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

design_patterns_in_typescript\factory_method> tsc --target ES5 .\demo.ts
design_patterns_in_typescript\factory_method> node .\demo.js
Method of ConcreteProductA
Method of ConcreteProductB

Benefits of Factory Design Pattern

Factory design pattern provides an approach to code for interface rather than implementation.
Factory pattern removes the instantiation of actual implementation classes from client code. Factory pattern makes our code more robust, less coupled, and easy to extend. For example, we can easily change PC class implementation because the client program is unaware of this.
Factory pattern provides abstraction between implementation and client classes through inheritance.