gistfile1.js

function Foo() {
   /* constructor stuff */
}

// apply a class prototype that includes private and public methods
(function () {

    function private(x) {
        return x + 1;
    }

    function wouldBePrivate() {
        return "I can't be overridden";
    }

    Foo.prototype = {
        public: function (n) {
            return "The answer is " + private(n);
        },
        protected: wouldBePrivate, // but now it's not
        usesProtected: function () {
            return "I said: " + wouldBePrivate();
        },
        usesAPIToProtected: function () {
            return "Whaddayano, " + this.protected();
        }
    };
})();

var f = new Foo();
f.public(41); // The answer is 42
f.protected(); // I can't be overridden
f.usesProtected(); // I said I can't be overridden
f.usesAPIToProtected(); // Whaddayano, I can't be overridden

f.protected = function () {
    return "I've been overridden!!!";
}
f.usesProtected(); // I said I can't be overridden
f.usesAPIToProtected(); // Whaddayano, I've been overridden!!!


// Alternately
var Foo;
(function () {

    Foo = function () {...}

    // private/protected functions here

    Foo.prototype = { ... }
})();

// or
var Foo = (function () {
    function Foo() {...}

    // private/protected functions here

    Foo.prototype = {...}

    return Foo;
})();

// or (don't do this one)
var Foo = new function () {
    function Foo() {...}

    // private/protected functions here

    Foo.prototype = {...}

    return Foo;
};