The inner workings of profile.js aren't explained at all in this course segment :(

Hi there,

I'm still slightly confused about the profile.js file. It seems to be everything we covered in the last section, with the exception of the Event Emitter. What exactly is this doing and how is this benefiting our program? I tried searching the docs but couldn't truly understand the importance.

Thanks, James.

The EventEmitter is the "class" or "object" that we are inheriting methods from. To do this we are using

util.inherits( Profile /* child constructor*/, EventEmitter /* parent constructor*/);
//&&
EventEmitter.call(this)

var profileEmitter = this;

This allows us to access EventEmitter methods and the profileEmitter allows us to refer to "this" within anonymous functions that we have created ("this" within an anon function or "callback" refers to the anon function and not the parent function that it is nested in) The EventEmitter allows us to expose events for the Profile function (or class) using the "emit" method.

profileEmitter.emit("eventName", eventDataForCallBack);

this means that with our studentProfile we can use the "on" method to tie a callback function to the "eventName" we specified

studentProfile.on("eventName", function(eventDataForCallBack) { 
    console.log(eventDataForCallBack); 
});

However nowadays we have ES6 classes so we dont need to do this loophole anymore, we can just extend the class like so

var EventEmitter = require("events").EventEmmiter

class Profile extends EventEmitter{

}

and this will allow "this" to be used to expose the eventemitter methods

Mr.Chalkers, please respond to these messages.

I agree too. profile.js needs some explanation...

agree 10000% --where is the explanation of the profile.js file?

Andrew Chalkley do something about it. At least put something in the teacher's notes!!!!!!

    var studentProfile = new Profile(username);

    studentProfile.on("end", function(profileJSON) {
      //show profile

      //store the values we need
      var values = {
        avatarUrl: profileJSON.gravatar_url,
        username: profileJSON.profile_name,
        badges: profileJSON.badges.length,
        javascriptPoints: profileJSON.points.JavaScript
      }
      //simple response
      response.write(`${values.username} has ${values.badges} badges\n`);
      response.end('Footer\n')
    });

What is being stored in the studentProfile variable? What is being passed into the profileJSON parameter on the callback function? I understand that it is a JSON object but profileJSON is never declared. Where does it come from and how is it automatically passed into the callback?

A video explaining the inner workings of profile.js could help clear up some of the confusion here.