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Design Pattern

Decorator

Wrap an object to add behavior without changing the original class.

structural

Visual Diagram

Base service
-> Auth wrapper
-> Log wrapper
-> Cache wrapper

When To Use

  • ->Adding logging, caching, or auth around services
  • ->Express-style middleware layers
  • ->Extending behavior without subclass explosion
Used in: Express middleware, NestJS decorators, service wrappers
decorator.js

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Output

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