Return an object from an object method in javascript

Question

A = {
    f1: function() {
        return {
            a: function(){ alert('sss'); }
        }
    }
}

A.f1().a();

Why is it used in this way?

Why is the method a() bound to A.f1()?

I really don't understand what the question is... Is something not working the way you expect it to? — J. Holmes
– J. Holmes, Commented Sep 5, 2012 at 2:21
I used to think 'A.f1().a()' shouldn't work,because method a() is not belong to f1(). — HACK21
– HACK21, Commented Sep 5, 2012 at 2:29
a does not belong to the function f1, it belongs to the value returned by invoking f1. — J. Holmes
– J. Holmes, Commented Sep 5, 2012 at 2:32

David G · Accepted Answer · 2012-09-05 02:29:15Z

1

Member function f1 of A returns an object literal with its member a set to a function. It could've also been written as:

A = {
   f1: {
        a: function() { alert('sss'); }
    }
}

A.f1.a();

Returning an object could in this case be personal preference. There is no functional difference between these two examples.

answered Sep 5, 2012 at 2:29

David G

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1 Comment

His is a sort of Factory method, while yours is Singleton type ?

Hasith · Accepted Answer · 2012-09-05 03:54:24Z

0

When you do as below:

var x = A.f1();

What you get on to x is the object returned by the f1 function. which is:

{
   a: function(){ alert('sss'); }
}

now the object 'x' has function a() on it. You can call that function as:

x.a();

Which is exatly similar to:

A.f1().a();

answered Sep 5, 2012 at 3:54

Hasith

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