Events - EventEmitter - Event-Driven Architecture - in Node.js

The event-driven architecture allows asynchronous/synchronous programming, and your application becomes able to perform non-blocking/blocking operations.

EventEmitter class is part of the events module in Node.js.

EventEmitter Methods : .on, .emit (Triggers the event), .once(executes only once), removeListener(Removes Specific Event), .off etc..

Disadvantages : Complex, Difficult to find error, Confusing, etc..

const EventEmitter = require('events');

// Initializing event emitter instances

var eventEmitter = new EventEmitter();

// Declaring listener fun1 to myEvent1

var function1 = (msg) => {

    console.log("Message from function1: " + msg);

};

// Declaring listener fun2 to myEvent2

var function2 = (msg) => {

    console.log("Message from function2: " + msg);

};

// Listening to myEvent with fun1 and fun2

eventEmitter.addListener('myEvent', function1);

// fun2 will be inserted in front of listeners array

eventEmitter.prependListener('myEvent', function2);

// Listing listeners

console.log(eventEmitter.listeners('myEvent'));

// Count the listeners registered to myEvent

console.log(eventEmitter.listenerCount('myEvent'));

// Triggering myEvent

eventEmitter.emit('myEvent', 'Event occurred');