CODEWITHSUNDEEP
javascriptclosures
Mozein
Mozein

Reputation: 807

Closures Cannot access a function

I am trying to understand closures. In the code below, I create an instance of the constructor function Ninja and I call the instance kawazaki. I expected to be able to access the methods of Ninja. However, I am getting a TypeError: Object #<Ninja> has no method 'feints' instead.

The output I expected was 1.

Here is my code:

function Ninja() {
    var feints = 0;

    function getFeints() {
        return feints;
    }

    function feints() {
        feints++;
    }
}

var kawazaki = new Ninja();

kawazaki.feints();

console.log(kawazaki.getFeints());

Upvotes: 0

Views: 49

Answers (3)

Mayur Buragohain
Mayur Buragohain

Reputation: 1615

Closure is a very simple yet largely misunderstood topic. 

function Ninja() {
    var feints = 0;

    function getFeints() {
        return feints;
    }

    function feintsInc() {
        feints++;
    }

}

You have defined the closure alright but please note that a closure is not actually a method of the object. In order to get your desired output you need to call the closures just before closing the object.

feintsInc();
getFeints();

If,however, you wish to do it as 

kawazaki.feintsInc();

you need to use this keywords in your function to get the functions assigned to the object.

Note,make sure your functions and variable names don't overlap.

Upvotes: 0

Ga&#235;l Barbin
Ga&#235;l Barbin

Reputation: 3919

The scope of the functions getFeints and feints is limited to the function Nija. As you can not access to variables declared in a function, you can not access to those functions.

To be able to execute kawazaki.feints(), you have to "attach" the function to the Ninja function, as an object (which a function also is)

You will find in these resources several ways to achieve that, and also some deeper explanations:

Upvotes: 0

Aadit M Shah
Aadit M Shah

Reputation: 74204

Try this instead:

var kawazaki = new Ninja;

kawazaki.feints();

alert(kawazaki.getFeints());

function Ninja() {
    var feints = 0;

    this.getFeints = function () {
        return feints;
    };

    this.feints = function () {
        feints++;
    };
}

You need to assing public properties to this within the constructor function.

Upvotes: 2

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