Why is the call() function not working with an object created with an already created class

Question

I am a javaScript beginner. I was trying to run a call function to an object which I created using a class. I expected an output - "Virat Kohli" with the following code :

    class person {
constructor(firstName,lastName){
    firstName = this.firstName;
    lastName = this.lastName
}
}


perFullName = {
    fullName : function(){
        return this.firstName + " " + this.lastName;
    }
}

const vk = new person("Virat","Kohli");
console.log(perFullName.fullName.call(vk))

But this returned me undefined undefined in my VS code console, but when I replaced it and created the object like this :

const vk = {
    firstName : "Virat",
    lastName : "Kohli"
}

It returned the expected output.

Can you please tell me the reason and how I can fix it?

Answer 1

The variable assignments in the constructor are back-to-front, they should assign the input values to the member variables.

Your fullName function can be moved into the class as a read only property getter:

class person {
    constructor(firstName, lastName){
        this.firstName = firstName;
        this.lastName = lastName
    }
    
    get fullName() {
        return this.firstName + " " + this.lastName;
    }
}

const vk = new person("Virat", "Kohli");
console.log(vk.fullName);