Why my function is not able to access the global object in Nodejs

Question

When executing this function in the browser I get a correct and expected message

function displayInformation() {
  console.log("student with " + this.rollNo + " is " + this.name + " who is in class: " + this.class + " and he is of " + this.subject + " stream ")
};

var student1 = {
  rollNo: 100,
  name: "Rajiv",
  class: 10,
  subject: "PCMC",
  display: displayInformation
};

var student2 = {
  rollNo: 101,
  name: "Sam",
  class: 11,
  subject: "PCMB",
  display: displayInformation
};

var student3 = {
  rollNo: 102,
  name: "Ghanshyam",
  class: 12,
  subject: "commerce",
  display: displayInformation
};

student1.display();
student2.display();
student3.display();

this.name = "Raju";
this.age = 28;
this.rollNo = 103;
this.class= 123;
this.subject = "Arts";

displayInformation();

However when executing this code in Nodejs I am getting undefined in the last sentence:

student with 100 is Rajiv who is in class: 10 and he is of PCMC stream
student with 101 is Sam who is in class: 11 and he is of PCMB stream
student with 102 is Ghanshyam who is in class: 12 and he is of commerce stream
student with undefined is undefined who is in class: undefined and he is of undefined stream

Why is the result not the same in Nodejs and the Browser?

Please post your code with code formatting, the quotation formatting has wrapped all the lines and destroyed the indentation. — Barmar, Apr 23 '19 at 15:48
You don't have add `>` before every line. Paste your code, select it, click on the `{ }` icon. Please read [How to create a Minimal, Complete, and Verifiable example](https://stackoverflow.com/help/mcve) and [How do I create a stack snippet?](https://meta.stackoverflow.com/questions/358992) — adiga, Apr 23 '19 at 15:51
I get `student with 103 is Raju who is in class: undefined and he is of Artsstream` in Chrome. You never assigned to `this.class`, so it's undefined. — Barmar, Apr 23 '19 at 15:51
I am sorry as i am new to stackoverflow, i will keep make sure this doesn't happens next time. but when i run the same code in VS code i am getting undefined for all the values, also after updating the value for class. — K.M.J, Apr 23 '19 at 15:59
How are you running this? From the console, or from a separate J's file? — Ferrybig, Apr 23 '19 at 16:03
It looks like he is running it in Nodejs, I just tested it and I am getting undefined too. I edited the question and added the node.js tag — Lolpez, Apr 23 '19 at 16:17
See [this](https://stackoverflow.com/questions/3127429/how-does-the-this-keyword-work) post. You can convert displayInformation to an arrow function and it will work as you want it to. — Mika Sundland, Apr 23 '19 at 16:33
You can also look at [this](https://stackoverflow.com/questions/22770299/meaning-of-this-in-node-js-modules-and-functions) post. It is specific for Node. — Mika Sundland, Apr 23 '19 at 16:40

Lolpez · Accepted Answer · 2019-04-23T16:19:43.423

2

The last line actual result is:

student with 103 is Raju who is in class: undefined and he is of Arts stream

The undefined is because you didn't assign a value to this.class

function displayInformation() {
  console.log("student with " + this.rollNo + " is " + this.name + " who is in class: " + this.class + " and he is of " + this.subject + " stream ")
};

this.name = "Raju";
this.age = 28;
this.rollNo = 103;
this.subject = "Arts";
this.class = 123; // <-- You missed this

displayInformation();

Also I really recommend to not use the this global object, I am not sure why are you using it.

edited Apr 23 '19 at 16:19

answered Apr 23 '19 at 16:02

Lolpez

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8
17

when i run the same code in VS code i am getting undefined for all the values in the terminal, also after updating the value for class – K.M.J Apr 23 '19 at 16:04
Are you executing nodejs? or just a browser javascript file? – Lolpez Apr 23 '19 at 16:05
I just executed it in Nodejs and you are right, I am getting undefined in the terminal, if you let me I can edit your question. – Lolpez Apr 23 '19 at 16:08

Why my function is not able to access the global object in Nodejs

1 Answers1