What Is Design Patterns?
Software Design Patterns
Design patterns are reusable solutions to common software design problems. The classic 'Gang of Four' book defines 23 patterns across three categories: creational (how objects are made), structural (how objects are composed), and behavioral (how objects communicate). Modern patterns extend beyond OOP.
How Design Patterns Works
Observer pattern: React's useState is an observer — state changes notify the UI to re-render. Strategy pattern: passing different sort functions to Array.sort(). Factory pattern: createServer() returns an HTTP server without exposing the constructor. You use patterns daily without naming them.
Don't force patterns where they don't fit. A simple function doesn't need a Strategy pattern. Direct code is often better than a pattern applied prematurely. Patterns should simplify, not complicate.
Key Concepts
- Singleton — Ensure a class has only one instance — database connections, configuration managers
- Observer — Objects subscribe to events and react to changes — event emitters, React state
- Factory — Create objects without specifying exact classes — abstract construction logic
- Strategy — Swap algorithms at runtime — pass different functions for different behaviors
Frequently Asked Questions
Do I need to memorize all 23 patterns?
No. Learn Singleton, Observer, Factory, Strategy, and Decorator. You'll encounter others as needed. Understanding the principles matters more than memorizing patterns.
Are design patterns still relevant?
The GoF patterns are OOP-heavy and some feel dated. But the underlying principles — loose coupling, single responsibility, composition — are timeless. Modern patterns (middleware, hooks, pipelines) are equally important.