8-event-emitter.md

Event-Emitter

• Pub/Sub pattern (similar to callbacks)
• Asynchronous handler function contains the payload
• EventEmitter-Module

// Import events module
const EventEmitter = require('events');

// Create an eventEmitter object
const eventEmitter = new EventEmitter();

Example

• addListener('eventname', listener)
• on('eventname', listener)
• once('eventname', listener)
• emit('eventname', [arg1], [arg2], [...])
• removeListener('eventname', listener)
• removeAllListeners(['eventname'])
• setMaxListeners(n)
• listeners('eventname')
• listenerCount(emitter, 'eventname') (Class Method)