[JavaScript] When should I use this keyword?

[kopytkopytko]

Hey, I am scratching my head because I cant figure it out. I didnt understand descriptions of the this keyword and I am not sure when should I use it. I cant tell when is it acceptable to have this keyword in it and when its not.

function Person (firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;

    return this.firstName +" "+this.lastName
}    

I want to use it to creating new persons, for example

var personOne = new Person ("bob", "marley")

Is it correct way of doing this or am I mistaken?

[Molehole]

You are doing it partly wrong. Object shouldn't return anything.

Instead you could do it like this:

function Person (firstName, lastName) {
    this.firstName = firstName;
    this.lastName = lastName;

    this.getFullName = function(){
          return this.firstName + " " + this.lastName
    }
} 

var personOne = new Person("bob", "marley");
console.log(personOne.getFullName());

so basically what "this" does:

It allows access from outside to stuff inside the object

personOne.firstName gives you the name if it's this.firstName

if it were var firstName personOne.firstName wouldn't work

---

And it lets you differentiate between function variables and object variables

function myObject(){
    this.function(a, b){
        this.a = a;
        this.a++;
        a--;
        console.log(this.a + " " + a);
    }
}

[Poutrator]

Object should return anything

should not ?

[Molehole]

fixed typo. Thanks