Why undefined? Even if the this pointer is pointing to the same object and also the strict mode is used

"use strict";
const data = {
firstName: "myName",
lastName: this.firstName,
};
console.log(data.lastName);

Output is undefined.
Can anyone explain why it’s happening?

>Solution :

Because this does not work like that. When you are defining your object literal (data), this does not point to that literal – to see what this actually is, do a console.log(this).

You can solve your problem by modifying your code like this:

"use strict";
const data = {
    firstName: "myName"
}
data.lastname = data.firstname;

Also, I recommend reading up on how this works to avoid confusion in the future – this is a bit weird in Javascript.