Can you name the main design patterns you have encountered in your practice?

Common design patterns encountered in Node.js practice:

• Singleton — ensures a class has only one instance and provides a global point of access to it.
• Factory — creates objects without specifying the exact class, allowing the type of object to be determined at runtime.
• Observer — allows objects to subscribe to events and receive notifications when they occur.
• Middleware — often used in Express.js to handle requests through a chain of functions.
• Decorator — dynamically extends the functionality of an object without changing its structure.

Example of Singleton in Node.js:

class Logger {
  constructor() {
    if (Logger.instance) {
      return Logger.instance;
    }
    Logger.instance = this;
  }
  log(message) {
    console.log(message);
  }
}

const logger1 = new Logger();
const logger2 = new Logger();
console.log(logger1 === logger2); // true

These patterns help in writing more structured, maintainable, and extendable code.