Question

155

Javascript Public/Private Variables

rated 0 times [ 156] [ 1] / answers: 1 / hits: 20733 / 13 Years ago, sat, october 8, 2011, 12:00:00

I have an object containing both public and private variables. The public variables are assigned to the private variables (I think), however, whenever I modify the private variables with a function, the public variables don't update.

var foo = (function() {

    //Private vars

    var a = 1;



    return {

        //Public vars/methods

        a: a,

        changeVar: function () {

            a = 2;

        }

    }

})();

alert(foo.a);  //result: 1

foo.changeVar();

alert(foo.a);  //result: 1, I want it to be 2 though

Now I know that if I change the line in changeVar to this.a = 2; it works but then it doesn't update the private variable. I want to update both the private and public variables at the same time. Is this possible?

JsFiddle showing problem

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aubriechantalr

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4 Years ago

answered 13 Years ago shylaelisan · Accepted Answer

When you set the a key in the object you're returning, that's making a copy of the 'private' a variable.

You can either use a getter function:

return {

    //Public vars/methods

    a: function() { return a; },

    changeVar: function () {

        a = 2;

    }

};

Or you can use Javascript's built-in accessor functionality:

obj = {

    //Public vars/methods

    changeVar: function () {

        a = 2;

    }

};

Object.defineProperty(obj, a, { get: function() { return a; } });

return obj;