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I am following a JavaScript tutorial in which the tutor runs a similar code as below. It's supposed to create a new property called age and set the value to (2022 - birth year).
Apparently, mine outputs undefined.

Anyone with an idea why?

const profile = {
name: "Michael",
level: 100,
birthYear: 2003,
calcAge() {
let age = 2022 - this.birthYear;
return age;
},
};

console.log(profile.calcAge());

const profile = {
name: "Michael",
level: 100,
birthYear: 2003,
calcAge() {
this.age = 2022 - this.birthYear;
return this.age;
},
};

console.log(profile.calcAge());

The two ways I posted will output the value of age.

You have to return the age from the function.

You also have to call the function: profile.calcAge()

@ op...Do you know about Scoping in Javascript? You can't access a variable located in a local scope outside its curly parenthesis.

TinubuFirstBorn:
const profile = {
name: "Michael",
level: 100,
birthYear: 2003,
calcAge() {
let age = 2022 - this.birthYear;
return age;
},
};

console.log(profile.calcAge());

@ OP this is what you need. In addition to that you are getting undefine because age is a local variable. Variables declared within a JavaScript function, become LOCAL to the function. They can only be accessed from within the function. Read more on local and global scope

this.age is not defined because it's defined in the function, when the function is called, age will be added to the property of the object. Hope that explains

Thanks to everybody TinubuFirstBorn jbreezy
efelico qtguru.
The code now works as expected after implementing your suggestions

arabmoney14:
I am following a JavaScript tutorial in which the tutor runs a similar code as below. It's supposed to create a new property called age and set the value to (2022 - birth year).
Apparently, mine outputs undefined.

Anyone with an idea why?

You need to do this before the console.log()
profile.calcAge();

you can do it as @TinubufirstBorn did. see below

The "this" keyword belongs to the Profile Object you define not the function. and Profile Object doesn't have any property call "age"

arabmoney14:
I am following a JavaScript tutorial in which the tutor runs a similar code as below. It's supposed to create a new property called age and set the value to (2022 - birth year).
Apparently, mine outputs undefined.

Anyone with an idea why?

First of all, there’s no object property called age, so what is this.age referencing?

In my example I create an object profile with some properties. I set age to 0, so I can calculate based on current year which I would be passing as a parameter in the calcAge function or method(a method is an object property that has a function).
Initially when I check the value of property, age is set to 0. But when I run profile.calcAge(2022), you can see the age changed to 24.

Apparently, what happened was that you did not call the function which was returning the age variable. You have to call the profile.calcAge() function before it can return the age variable.