5 Design Patterns Every Developer Should Know

Design patterns are proven solutions to common programming challenges. Understanding these patterns can significantly improve your code quality and maintainability.

Singleton Pattern

The Singleton pattern ensures a class has only one instance while providing global access to this instance.

class Database {
    private static instance: Database;

    private constructor() {}

    public static getInstance(): Database {
        if (!Database.instance) {
            Database.instance = new Database();
        }
        return Database.instance;
    }
}

Observer Pattern

Keep objects informed of changes without tightly coupling them together.

class EventEmitter {
    private listeners = {};

    subscribe(event, callback) {
        if (!this.listeners[event]) {
            this.listeners[event] = [];
        }
        this.listeners[event].push(callback);
    }

    emit(event, data) {
        if (this.listeners[event]) {
            this.listeners[event].forEach(callback => callback(data));
        }
    }
}

Factory Pattern

Create objects without explicitly specifying their exact classes:

class UserFactory {
  createUser(type) {
    switch (type) {
      case "admin":
        return new AdminUser();
      case "regular":
        return new RegularUser();
      default:
        throw new Error("Invalid user type");
    }
  }
}