Question

I pass an object literal into a framework method called supportP(). This object literal has a special property called _p which denotes that the members of it are private. From with in the object literal it can be accessed via this._p. However when I pass the object literal into the “outer” scope I do not copy _p. It has now been made private by omission. In order to access _p from public member methods I bind them to the original object using bind() so they still have access to _p via this.

Will this work? Are there other things to consider? Wanted some feedback before I tested it out.

Below are relevant snippets.

/*$A.supportP
**
**
**
*/
$A.supportP = function (o, not_singleton) {
    var oo
        key;
    SupportList[o.Name] = {};
    if (not_singleton) {
        // ignore this section
    } else { // *look here - isFunc returns true if a function
        for (key in o) {
            if ((key !== '_p') && (isFunc(o[key])) {
                oo[key] = o[key].bind(o);
            } else if (key !== '_p') {
                oo[key] = o[key];
            } else {
                // private (_p) - anything to do here?
            }
        }
        return oo;
    }
};


/*$A.test
**
**
**
*/
var singleton_object = $A.supportP({
    _p: 'I am private',
    Name: 'test',
    publik_func: function () {
        // this will refer to this object so that it can access _p
        // this._p is accessible here due to binding
    }
}, false);

Answer 1

Will this work?

Yes, you will be able to access the “private” property via this._p.

Are there other things to consider?

You are cloning the object. Yet, the method on it has no access to it – it is bound to the “old” object whose properties will not reflect the changes on the copy. I am not sure whether this is by design or by accident.

---

For strict privateness, you will need to use closures with local variables. Properties can never be made private.

var singleton_object = (function() {
    var _p = 'I am private'; // local variable
    return {
        Name: 'test',
        publik_func: function () {
            // this will refer to this object so that it can access the properties
            // _p is accessible here due to closure, but not to anything else
        }
    };
}()); // immediately-executed function expression

---

Another solution, using two distinct objects (one hidden) which are passed into a framework method:

function bindPrivates(private, obj) {
    for (var key in obj)
        if (typeof obj[key] == "function")
            obj[key] = obj[key].bind(obj, private);
    return obj;
}

var singleton_object = bindPrivates({
    p: 'I am private'
}, {
    Name: 'test',
    publik_func: function (_) {
        // this will refer to this object so that it can access "public" properties
        // _.p, a "private property" is accessible here due to binding the private 
        //  object to the first argument
    }
});