Nodejs: How to handle event listening between objects?

Question

I currently have the problem that I have an object which should listen on another object.

The question is: how should I handle the subscription? Currently, I only know o

Answer 1

Edit

Per your comment, I'm not sure what you find unreadable about this, but you can try using Stream objects and the elegant Stream#pipe method.

The Streams

var Stream = require('stream').Stream;
var util = require('util');

var Sender = function() {
  this.readable = true;
  this.saySomething = function(message) {
    this.emit('data', message);
  };
};
util.inherits(Sender, Stream);

var Receiver = function() {
  this.writable = true;
  this.write = function(message) {
    console.log('received: ' + message);
  }
};
util.inherits(Receiver, Stream);

Usage

// instance of each
var s = new Sender();
var r = new Receiver();

// connect using pipe!
s.pipe(r);

// an event
s.saySomething('hello world'); //=> received: hello world

I particularly like using Stream objects. The pipe method is quite handy :) Each stream has a single input and output. I like them because it encourages you to build small, functional components that are responsible for a specific task. Then, you can chain/reuse them however you see fit.

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Original post

You'll want to use EventEmitter

Here's a quick example

var events = require('events');
var util = require('util');

var SampleEmitter = function() {
    events.EventEmitter.call(this);

    this.sayHello = function() {
      this.emit('hello', 'hello world');
    };
};
util.inherits(SampleEmitter, events.EventEmitter);

var SampleListener = function(emitter) {
    emitter.on('hello', function(data) {
        console.log(data);
    });
};

var se = new SampleEmitter();
var sl = new SampleListener(se);

se.sayHello(); //=> 'hello world'