What does events/EventEmitter do in a nodejs constructor function

Question

I am learning node.js. On the nodejs api website there is a piece of code that I don't really get. The link is here

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

function MyStream() {
    events.EventEmitter.call(this);
}

util.inherits(MyStream, events.EventEmitter);

MyStream.prototype.write = function(data) {
    this.emit("data", data);
}

var stream = new MyStream();

console.log(stream instanceof events.EventEmitter); // true
console.log(MyStream.super_ === events.EventEmitter); // true

stream.on("data", function(data) {
    console.log('Received data: "' + data + '"');
})
stream.write("It works!"); // Received data: "It works!"

so the confusing part is

events.EventEmitter.call(this);

What does it do here?

Answer 1

MyStream is a new object declaration that inherits behaviors from events.EventEmitter as can be seen from this line where the inheritance is configured:

util.inherits(MyStream, events.EventEmitter);

So, when the MyStream constructor is invoked usually via something like var stream = new MyStream();, it needs to also invoke the constructor of the object that it inherits from so the parent object can initialize itself properly. That's what this line is:

events.EventEmitter.call(this);

events.EventEmitter is the constructor of the object that MyStream inherits from. events.EventEmitter.call(this) instructs Javascript to call that constructor with the this pointer set to this object.

If you need more help with understanding .call(), you can read this MDN reference.