Question

Here is the code

function Person(name, age, weight) {
    this._name = name;
    this._weight = weight;
    this._age = age;
}

Person.prototype = {
    Anatomy: {
        Weight: this._weight,
        Height: (function () {
            //calculate height from age and weight
        })
    }
}

i expected Anatomy.weight to be 60 when i ran this code:

var x = new Person('jack',24,60);
console.dir(x.Anatomy);

To my surprise it was undefined. On inspection it seemed that this was referring to global object window. Now what has happened here 🙁
I expected this._weight to refer Person objects weight, otherwise from rough calculation, this should have at the least referred to Anatomy since it is a object. Could someone clarify the doubt

Answer 1

You can’t to that. this is only available in functions. Where you used it, it refers to the global object. A possible solution would be this:

function Anatomy(weight) {
    this.Weight = weight;
    this.Height = [...];
}

function Person(name, age, weight) {
    this._name = name;
    this._weight = weight;
    this._age = age;
    this.Anatomy = new Anatomy(this._weight);
}

I don’t know if this is the best solution, but it’s the best that I can think of right now.