Observer Pattern

This walks you through implementing the classic observer pattern for event-driven pub/sub communication in JavaScript and TypeScript. You get a straightforward Observable class with subscribe, unsubscribe, and notify methods, plus a practical React example showing how to decouple event handlers from multiple listeners like loggers and toast notifications. The guidance from patterns.dev is solid on when to use this (multiple components reacting to state changes) and when to skip it (high subscriber counts or when simple callbacks would do). It mentions RxJS as the production-grade option if you need more power, but the vanilla implementation here is enough for understanding the fundamentals and handling basic decoupled communication.