How to call function A from function B within the same namespace?

Question

Let's say I have the namespace,

var Namespace = {
    A : function() {
        alert('Hello!');
    },
    B : function() {
        // Call A() from here, do other stuff
    }
}

In this namespace, I intend for A to be a helper function to B. That is to say, A() will never be called outside the namespace. It will only be called by the functions within the namespace.

What's the best way to address the issue of a local/helper function within a namespace? The way I see it there are two possibilities:

// Method #1    
var Namespace = {
    A: function() {
        alert('Method #1');   
    },

    B : function() {
        Namespace.A();
    }
}

Namespace.B();

// Method #2
function Namespace2() {
    var A = function() {
        alert('Method #2');
    };

    this.B = function() {
        A();        
    }
}

var ns2 = new Namespace2();
ns2.B();

In the first method, it is ugly and awkard to type Namespace.A() (repeatedly) in every function within the namespace. This leads me to prefer Method #2. But I was curious what was the best practice here.

Hubro · Accepted Answer · 2013-07-22 15:17:51Z

13

I recommend placing the "namespace" inside a function scope. Everything not explicitly public will be naturally private:

var Namespace = (function() {
    var self = {};

    // Private
    var A = function() {
        ...
    };

    // Public
    self.B = function() {
        A();
    }

    return self;
}());

Namespace.B(); // Works
Namespace.A(); // Doesn't work

answered Jul 22, 2013 at 15:17

Hubro

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6 Comments

ktm5124 Over a year ago

This is a nice solution. My question is, does Namespace redefine its functions every time you access it? If so, it would be a bad use of memory.

Hubro Over a year ago

@ktm5124: No. The function is run immediately and the object self is assigned to Namespace.

Naftali Over a year ago

@Codemonkey in your case you cannot make multiple Namespace objects.

Hubro Over a year ago

@Neal: I don't follow. Why would you make instances of a namespace?

snowYetis Over a year ago

This is the most underrated post I have come across.

|

Comfortably Numb · Accepted Answer · 2013-07-22 15:06:49Z

6

You can call it using this statement

this.A();

answered Jul 22, 2013 at 15:06

Comfortably Numb

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3 Comments

Hubro Over a year ago

This is not guaranteed to call Namespace.A.

ttt Over a year ago

@Hubro if i write namespace instead of Namespace, it works for me.

ccpizza Over a year ago

this will depend on the context; if you are inside an event handler then this will not point to the top-level namespace so Namespace.A is more predictable inside nested scopes.

Naftali · Accepted Answer · 2013-07-22 15:07:26Z

2

Well you can event use a third option where the Namespace is created in it's own scope:

var Namespace = (function(){
    var A = function() {
        alert('scoped method');
    };

    function Namespace() {

          var A1 = function() {
               alert('Namespace "private" method');
          };

          Namespace.prototype.B1 = function(){
              A();  //will run
              A1(); //will run with no errors
          };

    };

    Namespace.prototype.B = function(){
        A();  //will run
        A1(); //ERROR!
    };

    return Namespace;
})();

answered Jul 22, 2013 at 15:07

Naftali

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2 Comments

ktm5124 Over a year ago

Thanks Neal, though I have the same question that I asked CodeMonkey in his response. That is, does Namespace redefine its functions every time you access it?

Naftali Over a year ago

@ktm5124 in my case it does not. All you have to do is new Namespace everything else is already defined. You can technically do Namspace.__proto__.B(); and it will still run without the new part.

Hubro · Accepted Answer · 2013-07-22 15:07:22Z

1

If you only intend to use A inside B, why not define it inside B?

var Namespace = {
    B: function() {
        var A = function() {
            ...
        }

        A();
    }
};

Namespace.B();

answered Jul 22, 2013 at 15:07

Hubro

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1 Comment

ktm5124 Over a year ago

I actually intend to use A inside B, C, D, E, ... that is, all of the public namespace functions, which are many. (I have omitted them and only included B.)

Chau Phu Cuong · Accepted Answer · 2015-05-15 08:19:29Z

-2

var Namespace = {
    A : function() {
        alert('Hello!');
    },
    B : function() {
        Namespace.A();
    }, 
}

note the Semi-colon at the end

edited May 15, 2015 at 8:19

answered May 14, 2015 at 17:08

Chau Phu Cuong

11 bronze badge

3 Comments

abarisone Over a year ago

Could you please add more details about the solution you provide?

ohmu Over a year ago

The comma at the end? What does the comma (},) after B's function have to do with anything?

Chau Phu Cuong Over a year ago

sorry, my english is not good. I want say it is Semi-colon ( , ). I note Semi-colon used to reply comma ( ; ) in snamepace <== GOOGLE STRANSLATE . I still code same that way and it is working .

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