Design Patterns - E-commerce Examples (Typescript)

Purpose

• A teaching/reference repository that holds one module per design pattern (GoF) implemented as examples in the context of an e-commerce application.
• Each pattern folder contains a lightweight TypeScript stub and metadata linking the pattern to a concrete e-commerce responsibility. Implement the pattern inside the stub when you want to create the example.

Why this topic

• E‑commerce systems contain many interacting parts — orders, payment, cart, inventory, shipping, promotions, notifications — which make it possible to illustrate all creational, structural and behavioral patterns naturally.

Repository Layout

• src/patterns/<pattern>/index.ts — stub for the pattern, exports metadata and a placeholder implementation entry.
• src/patterns/index.ts — exports a map of all pattern modules (used by tests/example).
• src/index.ts — small demo that prints pattern mapping (after build or with ts-node).
• tests/patterns.test.ts — simple test asserting all pattern modules exist.

Desing Patterns Mapping (GoF) -> E-commerce example

• Creational
  • Singleton: ConfigurationManager (global config, DB connection single instance)
  • Factory Method: PaymentFactory (create payment method handlers)
  • Abstract Factory: ShippingFactory (factories for domestic/international shipping)
  • Builder: OrderBuilder (construct complex Order objects)
  • Prototype: CartItem.clone (clone items with modifiers)
• Structural
  • Adapter: PaymentGatewayAdapter (adapts external gateway API)
  • Bridge: Notification (abstraction) & NotificationSender (implementations)
  • Composite: ProductCategory / ProductBundle (tree of product items)
  • Decorator: PriceDecorator (add taxes, discounts)
  • Facade: CheckoutFacade (simplify checkout subsystem)
  • Flyweight: ProductImageFlyweight (share image data across products)
  • Proxy: InventoryProxy (lazy/remote inventory checks)
• Behavioral
  • Chain of Responsibility: OrderProcessingPipeline (validation -> payment -> shipping)
  • Command: CartCommands (add/remove/undo)
  • Interpreter: PromoCodeInterpreter (interpret discount expressions)
  • Iterator: CatalogIterator (iterate over catalogs)
  • Mediator: CheckoutMediator (coordinates cart, payment, shipping)
  • Memento: OrderMemento (save/restore order state)
  • Observer: InventoryObserver / Notification subscribers
  • State: OrderState (Pending -> Paid -> Shipped -> Cancelled)
  • Strategy: PricingStrategy (different pricing algorithms)
  • Template Method: PaymentProcessingTemplate (common workflow with hooks)
  • Visitor: ReportingVisitor (traverse products/orders to build reports)

How to run locally

1. Clone or create repository:

   • Create locally and commit these files, or use GitHub CLI:
     • gh repo create / --public --source=. --remote=origin --push

2. Install dependencies:

   • npm install

3. Build:

   • npm run build

4. Run demo:

   • npm start
   • or in development: npm run dev

5. Run tests:

   • npm test

Notes

• Patterns are intentionally left as stubs. Each stub exports name and description metadata plus a placeholder example() function you can implement.
• Tests validate that all pattern modules exist. Add more unit tests as you implement each pattern.

Contributing

• Follow the folder naming convention: src/patterns/<lowercase-name-with-hyphens>.
• Add pattern-specific README and tests inside each pattern folder as you implement.

License

• Add your preferred license (MIT recommended). This repo is a template.