"Static methods" of the EventEmitter()

Question

I am new to Nodejs, and I have a question about the EventEmitter's listenerCount() method, but also the way of calling static methods in general. This is the sample code from TutorialsPoint's Nodejs tutorial on the event emitter:

var events = require('events');
var eventEmitter = new events.EventEmitter();

// listener #1
var listner1 = function listner1() {
   console.log('listner1 executed.');
}

// listener #2
var listner2 = function listner2() {
  console.log('listner2 executed.');
}

// Bind the connection event with the listner1 function
eventEmitter.addListener('connection', listner1);

// Bind the connection event with the listner2 function
eventEmitter.on('connection', listner2);

var eventListeners = require('events').EventEmitter.listenerCount
   (eventEmitter,'connection');
console.log(eventListeners + " Listner(s) listening to connection event");

// Fire the connection event 
eventEmitter.emit('connection');

// Remove the binding of listner1 function
eventEmitter.removeListener('connection', listner1);
console.log("Listner1 will not listen now.");

// Fire the connection event 
eventEmitter.emit('connection');

eventListeners = require('events').EventEmitter.listenerCount(eventEmitter,'connection');
console.log(eventListeners + " Listner(s) listening to connection event");

console.log("Program Ended.");

It calls the listenerCount() method on the events "class" (is it a class?) by requiring the events again. I am referring to the part where it says:

var eventListeners = require('events').EventEmitter.listenerCount (eventEmitter,'connection')

listenerCount() is essentially a static method, I suppose, since you cannot call it on the events object directly.

(I also don't quite understand why the implementation is such, and why wouldn't it be implemented so that I could invoke it on my eventEmitter object, such as: eventEmitter.listenerCount('connection'))

But either way, what I have then tried, is to call this static method on my events object, without the additional require call (on both instances in this code), so that it looked like this:

events.EventEmitter.listenerCount(eventEmitter, "connection");

And the output of the program was the same.

So my question about this is, is there an actual reason the author called it by making a new require for each of those calls, and is there (or could there be) any difference in the behavior of the way the calls were made in the original code, and my alteration?

Answer 1

FWIW you can actually use emitter.listenerCount() directly since at least node v4.0.0.

As for the extra require(), it's not needed and you can do what you have suggested (events.EventEmitter.listenerCount()).

Answer 2

It is not a class. There are no classes in JavaScript. There is a class keyword in ES6 but it is a syntax sugar for objects and prototypes.

And for that reason there is really no distinction between static and instance methods in JavaScript because every method is an instance method. You cannot call a method on anything else than an object. And EventEmitter is an object, but it is also a constructor function for other objects.

Also, this:

var x = require('module').a.b();

is the same as:

var module = require('module');
x = module.a.b();

It's not just the same result but actually the same object - every required module is evaluated only once and cached, and every require of the same modules gives you the same object.

You can even pass data between modules that way.

require('module').x = 1;
console.log(require('module').x);