Developer Implements Observer, Singleton, and Factory Patterns in JavaScript

A developer documented their Week 6 learning task focused on three widely used JavaScript design patterns: Observer, Singleton, and Factory. The Observer pattern was implemented as a custom event emitter supporting subscribe, unsubscribe, single-use, and trigger methods, modeled on real-world notification systems like YouTube. The Singleton pattern was applied to a configuration manager, ensuring only one shared instance exists across the entire application. Each pattern was tested using Node.js's built-in assert module to validate practical behavior rather than relying solely on theory. The write-up also notes that while these patterns solve common design problems, overuse — particularly of Singleton — can reduce testability and maintainability.