How to build custom Node.js event emitters

The text discusses the concept and implementation of event emitters in Node.js, highlighting their role in enabling event-driven programming within the backend. It explains the distinction between system and custom events in Node.js, with system events handled by the libuv library and custom events managed by the EventEmitter class. The EventEmitter class, part of Node.js's core module, supports asynchronous, non-blocking I/O operations by enabling events to emit and be handled through associated listeners. The article further illustrates how to build a custom event emitter using a function constructor and prototypal inheritance, explaining key methods such as `on`, `emit`, and `listenerCount`. It emphasizes the importance of event emitters in the Node.js ecosystem, as they are integral to various Node.js objects like streams and the HTTP module, all of which rely on the EventEmitter class to handle events efficiently.