Core ModulesLesson 27Free preview

Events Module

This lesson is part of Node.js · All levels

Summary

The events module provides the EventEmitter class, the foundation of the event-driven pattern in Node.js. You can broadcast an event with a emitter and hear it on or once. Almost all of the asynchronous Node APIs, from streams to servers, are built on this pattern.

Key points

EventEmitter adds an event with on and broadcasts it with emitter
Once just executed the listener for the first call.
Listeners run in sequence according to the registration order
An event error without a listener could cause the process to crash.

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