Basic EventEmitter example

do_stuff.js

var SimpleQueue = require('./simple_queue');

// Set up our SimpleQueue instance
var queue = SimpleQueue();
queue.on(SimpleQueue.events.JobAdded, function(job) {
	console.log("A job was added:", job);
});
queue.on(SimpleQueue.events.NoJobs, function() {
	console.log("Someone wanted to get a job, but none were in the queue");
});
queue.on(SimpleQueue.events.Drain, function() {
	console.log("Someone just grabbed the last job!");
});
queue.on(SimpleQueue.events.JobFound, function(job) {
	console.log("Someone just grabbed a job:", job);
});


// Later on in this code, after we've gotten work to do (perhaps inside an Express app...)

queue.add('foo'); // Triggers JobAdded
queue.add('bar'); // Triggers JobAdded
queue.get(); // Triggers JobFound
queue.get(); // Triggers JobFound and Drain
queue.get(); // Triggers NoJobs

simple_queue.js

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

function SimpleQueue()
{
	return Object.create(SimpleQueue.prototype, {
		jobs: {
			value: [],
			writable: true,
			enumerable: true
		}
	});
}
util.inherits(SimpleQueue, EventEmitter);
SimpleQueue.events = {
	JobAdded: 'job_added',
	NoJobs: 'no_jobs',
	JobFound: 'job_found',
	Drain: 'drain'
};




SimpleQueue.prototype.add = function add(job)
{
	this.emit(SimpleQueue.events.JobAdded, job);
	this.jobs.push(job);
}


SimpleQueue.prototype.get = function get()
{
	if (this.jobs.length == 0) {
		this.emit(SimpleQueue.events.NoJobs);
		return null;
	}
	var job = this.jobs.shift();
	this.emit(SimpleQueue.events.JobFound, job);
	if (this.jobs.length == 0) {
		this.emit(SimpleQueue.events.Drain);
	}
	return job;
}


module.exports = SimpleQueue;