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JavaScript Node.js Basics (2014) Building a Command Line Application Perfecting: Getting Multiple Profiles

Posted by Haziq Mir
Haziq Mir
Courses Plus Student 4,656 Points

Getting "undefined" points when trying to access points for a topic.

I am trying to perfect the app as suggested in the teacher's notes. I can't, however, get the app to fetch points in a topic specified by the user. Here is my code:

// index.js

var profile = require("./profile");
var topic = process.argv.slice(2,3);
var users = process.argv.slice(3);

if (users.length > 0) {
    users.forEach(function(user){
        profile.get(user, topic);
    });
} else {
    console.log("Please type in a user name, like this: node index.js <username1>, ...");
}

// index.js

var profile = require("./profile");
var topic = process.argv.slice(2,3);
var users = process.argv.slice(3);

if (users.length > 0) {
    users.forEach(function(user){
        profile.get(user, topic);
    });
} else {
    console.log("Please type in a user name, like this: node index.js <username1>, ...");
}

// profile,js
var http = require("http");

// Print out message
function printMessage(username, badgeCount, points, topic) {
    var message = username + " has " + badgeCount + " total badge(s) and " + points + " points in " + topic + ".";
    console.log(message);
}

// Print out error
function printError(error) {
    console.error(error.message);
}

function getProfile(username, topic) {
    var request = http.get("http://teamtreehouse.com/" + username + ".json", function(response){
        // console.log(response.statusCode);
        var body = "";
        response.on('data', function(chunk) {
            body += chunk;
        });
        response.on('end', function() {
            if (response.statusCode === 200) {
                try {
                    // Parse the data
                    var profile = JSON.parse(body);
                    // Print the data
                    printMessage(profile.name, profile.badges.length, profile.points.topic, topic);
                } catch(error) {
                    // Parse Error
                    printError(error);
                }
            } else {
                // Status Code error
                printError({message: "There was an error getting the profile for " + username + ". (" + http.STATUS_CODES[response.statusCode] + ")"});
            }
        });
    });

    // Connection Error
    request.on('error', printError);
}

module.exports.get = getProfile;

1 Answer

Stefan Osorio
Stefan Osorio
16,419 Points
Stefan Osorio
Stefan Osorio
16,419 Points

Hi Haziq!

The problem lies in this line:

printMessage(profile.name, profile.badges.length, profile.points.topic, topic);

You are using dot notation to access the points of the selected topic. Dot notation is great because it's fast to write and easy to read, but in certain cases you have to use square bracket notation. Selection of properties with variables ("topic") is one of those cases.

This should work:

printMessage(profile.name, profile.badges.length, profile.points[topic], topic);
Andrew Chalkley
Andrew Chalkley
Treehouse Guest Teacher
Andrew Chalkley
Andrew Chalkley
Treehouse Guest Teacher

The square bracket notation is helpful when you want to programmatically access the key of an object for example...

var person = {
  "firstName": "Andrew",
  "lastName": "Chalkley"
}

function printValueFor(key) {
  console.log(person[key]);
}

printValueFor("firstName") //Andrew
printValueFor("lastName") //Chalkley

If you use dot notation person.key is undefined because it's looking for something like this:

var person = {
  "firstName": "Andrew",
  "lastName": "Chalkley",
  "key": "Do people have keys?"
}

So the square brackets are specifically used for these type of dynamically accessed values. Dot notation is used when you know the key you want to access and it's not dynamic (for example from user input).

Haziq Mir
Haziq Mir
Courses Plus Student 4,656 Points

Thanks for the help, guys! :)