Accessing private member variables from prototype-defined functions

Question

Is there any way to make “private” variables (those defined in the constructor), available to prototype-defined methods?

TestClass = function(){
    var priv         


        

Answer 1

I faced the exact same question today and after elaborating on Scott Rippey first-class response, I came up with a very simple solution (IMHO) that is both compatible with ES5 and efficient, it also is name clash safe (using _private seems unsafe).

/*jslint white: true, plusplus: true */

 /*global console */

var a, TestClass = (function(){
    "use strict";
    function PrefixedCounter (prefix) {
        var counter = 0;
        this.count = function () {
            return prefix + (++counter);
        };
    }
    var TestClass = (function(){
        var cls, pc = new PrefixedCounter("_TestClass_priv_")
        , privateField = pc.count()
        ;
        cls = function(){
            this[privateField] = "hello";
            this.nonProtoHello = function(){
                console.log(this[privateField]);
            };
        };
        cls.prototype.prototypeHello = function(){
            console.log(this[privateField]);
        };
        return cls;
    }());
    return TestClass;
}());

a = new TestClass();
a.nonProtoHello();
a.prototypeHello();

Tested with ringojs and nodejs. I'm eager to read your opinion.