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how to have Javascript Object creation pattern with Reusable methods and private properties?

Considering object creation patterns with private properties, one way to do is :
function MyStack (){
var list = [],
index = 0;
this.push = function(val){
return list[index++] = val;
};
this.pop = function(){// ...}
}
var stack1 = new MyStack(); stack1.push(5);
var stack2 = new MyStack(); stack2.push(11);
Problem with this: Every instance of Stack has it's own copy of methods 'push' and 'pop'.
Another way for implementing constructor method is:
function MyStack(){
this.list = [];
this.index = 0;
}
MyStack.prototype = {
insert: function(val){
return this.list[this.index++] = val;
},
pop:function(){//...}
}
Problem here: We lose the privacy of list and index.
Is there a way, such that we can have both methods reuse among instances and privacy of properties ?
I understand that we can have this for methods that don't operate on any state of the object, but I am talking more about those methods that do operate on the state.

Yes. I've edited this code so it's actually fully functional as you had intended it to work. It seems a bit redundant to me, but, it does provide you the ability to provide a public interface, but to keep your variables private and control the way the user interacts with them.
function MyStack(){
var list = [];
var index = 0;
this.getIndex = function(){
return index;
}
this.setIndex = function(val){
index = val;
}
this.list = function(val){
if(val){
// setter if a value was provided. Illustrating how you can control
// index, which I assume is the point of having these things private
// to begin with
return list[this.setIndex(this.getIndex() + 1)] = val;
}
// always return list - acts like a getter
return list;
}
}
MyStack.prototype = {
insert: function(val){
return this.list(val);
},
pop:function(){}
}
var stack1 = new MyStack();
stack1.insert(5);
var stack2 = new MyStack();
stack2.insert(11);

You should check out John Resig's Simple Javascript Inheritance. It is a great read, and it has been extended to provide support for privates, aptly called Privates.js;

A constructor function may return any object (not necesserily this). One could create a constructor function, that returns a proxy object, that contains proxy methods to the "real" methods of the "real" instance object. This may sound complicated, but it is not; here is a code snippet:
var MyClass = function() {
var instanceObj = this;
var proxyObj = {
myPublicMethod: function() {
return instanceObj.myPublicMethod.apply(instanceObj, arguments);
}
}
return proxyObj;
};
MyClass.prototype = {
_myPrivateMethod: function() {
...
},
myPublicMethod: function() {
...
}
};
The nice thing is that the proxy creation can be automated, if we define a convention for naming the protected methods. I created a little library that does exactly this: http://idya.github.com/oolib/

I think in both approaches you mentioned, When ever object is created using constructor pattern the properties will get copied to its objects. This you mentioned for the 1st approach as the concern. I feel the same will be applied for the second approach also along with your concern in this approach.
We generally go to the second approach you mentioned when ever we want to extend the properties of "MyStack" to some other class.
Lets say i want to extend your class MyStack to MyTest like below
var dummy = function();
dummy.prototype = MyStack.prototype;
var MyTest = function(){
};
MyTest.prototype = new dummy(); // Assigning MyStack properties to MyTest
var obj = new MyTest();

Implementing setter and getter in JavaScript object

I want to implement setter and getter on local
javascript variable. Here is an example function:
function someThing() {
var someLocalvariable = '';
}
// with this function I want to
// return value of someLocalvariable
// also if it is possible to implement
// setter in this way.
someThing.prototype.getLocalVar = function() {
}
I want variable to be 'realy' private. I don't wont
to use something like this:
someThing.prototype.someLocalvariable =
or
function someThing() {
this.someLocalvariable = '';
}
or attaching function inside someThing() like this:
function someThing() {
var someLocalvariable = '';
this.getLocalvariable = function() {
return someLocalvariable;
}
}
I would be very grateful for any guidance and assistance.

Your last example of what you don't want to do won't work (it has syntax errors), (it's been fixed) but I think you may have meant the usual way of doing this, which is to make the getter and setter closures within the constructor function (below).
Unfortunately, if you want truly private variables, this is just about your only option. There is no other way to get truly private, instance-specific variables. However, see "hack" below.
Here's the correct version of the usual way of doing this (which I think you said you don't want, but for completeness):
function SomeThing() {
var privateVar;
this.setPrivateVar = function(val) {
privateVar = val;
};
this.getPrivateVar = function() {
return privateVar;
};
}
// use:
var t = new Something();
t.setPrivateVar("foo");
console.log(t.getPrivateVar()); // "foo"
Like most, I first read of this pattern on Douglas Crockford's site.
This option does carry a downside: Every instance created via the SomeThing constructor function gets its own two functions. They cannot be shared between instances. So if there are going to be hundreds or thousands of SomeThing instances in your app, that's something to be considered from a memory perspective. If there are going to be a couple of hundred or fewer, it probably doesn't matter. (Those numbers are pulled out of a hat and you should not trust them, you'll have to review your code's memory use when/if there's some kind of issue; but you get the idea.)
The hack: If your instances will already have some kind of unique identifier on them as public data (or you're willing to add one, again it will be public), and if you're willing to add a fair bit of complication into the use of the instances, you can have a private cache that holds the data for all of your instances that only your code can access, and key into that cache via the unique identifier of the object. Like this (in this example, I'm allocating the id values, but you can use existing unique IDs if you have them):
var SomeThing = (function() {
var cache = {}, idAllocator = 0;
function SomeThing() {
this.id = ++idAllocator; // The unique identifier, can be a string if desired
cache[this.id] = {};
}
SomeThing.prototype.getPrivateVar = function() {
var data = cache[this.id];
return data && data.privateVar;
};
SomeThing.prototype.setPrivateVar = function(value) {
cache[this.id].privateVar = value;
};
SomeThing.prototype.destroy = function() {
delete cache[this.id];
};
return SomeThing;
})();
Here's how that works: All of the functions are closures over the cache local variable in the outer scoping function. We index into that using the unique ID of the object, which gives us an object on which we put our private data members. When the code using the instance is done using it, that code must call destroy (which is a major downside to this pattern) so we remove the private data object from cache by deleting the property for our id.
Caveats and costs:
You still have a public piece of data that is the key to your private data (id in the above)
Users of the instances created by SomeThing must call destroy on those instances when they're done with them. This is anathema to the way JavaScript's garbage handling works, but it's a requirement of the pattern above because otherwise you end up with cruft building up in the cache object.
(I wouldn't worry about this one) Eventually, if you're using the automatic id values above, you'll run out of them, if your app creates and destroys a lot of these instances. But JavaScript numbers go very high up indeed, and if that's an issue just find a different way to allocate IDs rather than the simplistic always-increasing system above.
I haven't had to use the pattern above in my work yet, but I expect there are use-cases for it involving thousands of SomeThing instances and thus the desire not to have per-instance functions.
Side note: In the above, I changed someThing to SomeThing. In JavaScript, the standard practice is for the names of normal functions to start with a lower-case letter, and for the names of constructor functions (ones you use with new) to start with a capital letter. Since SomeThing is meant to be used with new, I capped it. This is only convention, but it's an overwhelmingly popular one and, of course, it's used within the language definition itself (Date is a constructor, setHours is a function).

Use Object.defineProperty() in the function constructor in order to define your getter and setter more info here..
To make truly private (not visible to the outside) some values use a Closure,
more info can be found here.
In the following example we define a getter and setter for property temperature, where the inner "private" value is stored in a variable var temperature.
var temperature will never be visible/accessibly from the outside of Archiver() has it is a Closure.
Please note that this pattern works on ES5 as Object.defineProperty() it is not supported on ES3.
function Archiver() {
var temperature = null;
var archive = [];
Object.defineProperty(this, 'temperature', {
get: function () {
console.log('get!');
return temperature;
},
set: function (value) {
temperature = value;
archive.push({ val: temperature });
}
});
this.getArchive = function () {
return archive;
};
}
var arc = new Archiver();
arc.temperature; // 'get!'
arc.temperature = 11;
arc.temperature = 13;
arc.getArchive(); // [{ val: 11 }, { val: 13 }]

Something like this:
function Field(val){
var value = val;
this.getValue = function(){
return value;
};
this.setValue = function(val){
value = val;
};
}
var field = new Field("test");
field.value
// => undefined
field.setValue("test2")
field.getValue()
Check ref: http://ejohn.org/blog/javascript-getters-and-setters/

Douglas Crockford has written this on implementing private members in JavaScript

That's not possible. If you have a local variable in someThing(), the function you attach to the prototype can't read its value (it's private, remember?). Your last example is the normal solution to this problem, why isn't this good enough for you?

Try these two ways to achieve setter and getter
var address = {
street : "No street",
city : "No city",
state : "No state",
get getAddress()
{
return (this.street+","+this.city+","+this.state);
},
set setAddress(theAddress)
{
var part = theAddress.toString().split(", ");
this.street = part[0] || "";
this.city = part[1] || "";
this.state = part[2] || "";
}
};
address.setAddress = "27 Sus Road, Pune, MH";
console.log(address.getAddress);
//Other setter and getter
function Square(side)
{
this._side = side;
};
Square.prototype = {
set setSide(side){
this._side = side;
},
get getSide(){
return this._side;
},
get getArea(){
return (this._side * this._side);
}
};
var mySquare = new Square(10);
mySquare.setSide = 15;
console.log("Area of square is "+mySquare.getArea+" with side "+mySquare.getSide);

First method
var address = {
street : "No street",
city : "No city",
state : "No state",
get getAddress()
{
return (this.street+","+this.city+","+this.state);
},
set setAddress(theAddress)
{
var part = theAddress.toString().split(", ");
this.street = part[0] || "";
this.city = part[1] || "";
this.state = part[2] || "";
}
};
address.setAddress = "27 Sus Road, Pune, MH";
console.log(address.getAddress);
Second method
function Square(side)
{
this._side = side;
};
Square.prototype = {
set setSide(side){
this._side = side;
},
get getSide(){
return this._side;
},
get getArea(){
return (this._side * this._side);
}
};
var mySquare = new Square(10);
mySquare.setSide = 15;
console.log("Area of square is "+mySquare.getArea+" with side "+mySquare.getSide);

Object inheritance

function Foo() {
this.SayFoo = function() {
console.log('Foo');
};
}
function Bar() {
this.SayBar = function() {
console.log('Bar');
};
}
Foo.prototype = new Bar();
var fooBar = new Foo();
fooBar.SayBar();
This obviously works, but is it the correct way to do it?
Is there any way to make use of jQuery's $.extend or something similar in order to achieve the same inheritance results?
Including other frameworks besides jQuery is not an option in this case.

There are actually multiple ways to do inheritance in JavaScript: neoclassical, prototypal, and functional. Douglas Crockford has nothing but bad things to say about neoclassical inheritance—the method you have above, and the method most Java/C# developers think will be the most natural. The reason revolves around all the awkward things you have to do to get it right—setting the prototype, setting the constructor, etc. Also, setting the prototype to a new instance of the parent class, like you have above, is usually frowned upon strongly, I believe because it complicates handling parameters with the base ctor.
If you're really sold on the neoclassical method, here's a great link that really goes over it.
The key part I reproduce for you here:
function Inherit(sub,super){
var thinF = function(){};
thinF.prototype = super.prototype;
sub.prototype = new thinF();
sub.prototype.constructor = sub;
sub.super = super.prototype;
if( super.prototype.constructor == Object.prototype.constructor ){
super.prototype.constructor = super;
}
}
FWIW Here's an example of functional inheritance that also highlights something you don't get with the neoclassical method: encapsulation/information hiding.
function eventRaiser(protectedStuff) {
protectedStuff = protectedStuff || {};
var that = {};
var events = {}; //private
protectedStuff.raise = function(key) {
if (!events[key]) return;
for (var i = 0; i < events[key].funcs.length; i++)
events[key].funcs[i].apply(null, Array.prototype.slice.call(arguments, 1));
};
that.subscribe = function(key, func) {
if (!events[key])
events[key] = { name: key, funcs: [] };
events[key].funcs.push(func);
};
return that;
}
function widget() {
var protectedStuff = {};
var that = eventRaiser(protectedStuff);
that.doSomething = function() {
alert("doing something");
protectedStuff.raise("doStuffEvent");
};
return that;
}
$(function() {
var w = widget();
w.subscribe("doStuffEvent", function(){ alert("I've been raised"); });
w.doSomething();
w.protectedStuff.raise("doStuffEvent"); //error!!!!! raise is protected
w.raise("doStuffEvent"); //and this obviously won't work
});

Yes, setting prototype to an instance is the correct way to do it.

How should I look at structuring my JavaScript?

I'm having a little trouble working out how my JavaScript should be structured, etc..
My OOP skills in languages such as PHP, ActionScript 3 and so on are what I'm assuming to be on-par, but JS is lacking this which has thrown me off quite a bit in my learning.
I have a vague understanding of the prototype feature which I used a little in AS2 - I believe this is the closest I'll be able to get. At the moment, I'm laying out my code similar to this:
var slideshow =
{
property: value,
/**
* This is a method
*/
myMethod: function()
{
// do method things
}
};
// ------
slideshow.property ++;
slideshow.myMethod();
This all works okay, but it's void my ability to do something like:
var myslideshow1 = new Slideshow();
var myslideshow2 = new Slideshow();
myslideshow1.property = 10;
myslideshow2.property = 16;
I'm not sure on how to go about creating two different instances of one "object" I've created (in this case, slideshow).
I can't find any resources that explain the prototype feature in a way that makes sense.
Any pointers would be supoib.

Any javascript function can act as a constructor for a class, so try this:
function SlideShow(params) {
return {
property: value,
myMethod: function() {
//do method things
};
};
};
var slideshow1 = new SlideShow(params);
slideshow1.property = 10;
//etc.

I would frown apon using prototype to add methods to a class as there could be performance issues
Here is a sample class structure you could use. JavaScript classes are not much different the functions.
function MyItem(){
this.d = '';
this.clear = function( ) {
this.d = '';
}
}
var myItem = new MyItem( )
myItem.d = "test";
alert(myItem.d);
myItem.clear();
alert(myItem.d)
Some good reading here

You should avoid using the new operator, everything is public. A better way to do what you want to do, and have private variables and functions is to do the following:
var slideshow = function () {
var self = {};
var private_param = "hello";
var private_func = function(say) {
alert(say);
};
var method = function() {
private_func(private_param);
};
var param = 500;
self.method = method;
self.param = param;
return self;
// return object, with the method func and param param publicly accessible
// private_param and private_func are not accessible to the outside
};
var presentation = slideshow(); // new slideshow, you could edit to pass in init params
presentation.method(); // hello

JavaScript Object Id

Do JavaScript objects/variables have some sort of unique identifier? Like Ruby has object_id. I don't mean the DOM id attribute, but rather some sort of memory address of some kind.

If you want to lookup/associate an object with a unique identifier without modifying the underlying object, you can use a WeakMap:
// Note that object must be an object or array,
// NOT a primitive value like string, number, etc.
var objIdMap=new WeakMap, objectCount = 0;
function objectId(object){
if (!objIdMap.has(object)) objIdMap.set(object,++objectCount);
return objIdMap.get(object);
}
var o1={}, o2={}, o3={a:1}, o4={a:1};
console.log( objectId(o1) ) // 1
console.log( objectId(o2) ) // 2
console.log( objectId(o1) ) // 1
console.log( objectId(o3) ) // 3
console.log( objectId(o4) ) // 4
console.log( objectId(o3) ) // 3
Using a WeakMap instead of Map ensures that the objects can still be garbage-collected.

No, objects don't have a built in identifier, though you can add one by modifying the object prototype. Here's an example of how you might do that:
(function() {
var id = 0;
function generateId() { return id++; };
Object.prototype.id = function() {
var newId = generateId();
this.id = function() { return newId; };
return newId;
};
})();
That said, in general modifying the object prototype is considered very bad practice. I would instead recommend that you manually assign an id to objects as needed or use a touch function as others have suggested.

Actually, you don't need to modify the object prototype. The following should work to 'obtain' unique ids for any object, efficiently enough.
var __next_objid=1;
function objectId(obj) {
if (obj==null) return null;
if (obj.__obj_id==null) obj.__obj_id=__next_objid++;
return obj.__obj_id;
}

I've just come across this, and thought I'd add my thoughts. As others have suggested, I'd recommend manually adding IDs, but if you really want something close to what you've described, you could use this:
var objectId = (function () {
var allObjects = [];
var f = function(obj) {
if (allObjects.indexOf(obj) === -1) {
allObjects.push(obj);
}
return allObjects.indexOf(obj);
}
f.clear = function() {
allObjects = [];
};
return f;
})();
You can get any object's ID by calling objectId(obj). Then if you want the id to be a property of the object, you can either extend the prototype:
Object.prototype.id = function () {
return objectId(this);
}
or you can manually add an ID to each object by adding a similar function as a method.
The major caveat is that this will prevent the garbage collector from destroying objects when they drop out of scope... they will never drop out of the scope of the allObjects array, so you might find memory leaks are an issue. If your set on using this method, you should do so for debugging purpose only. When needed, you can do objectId.clear() to clear the allObjects and let the GC do its job (but from that point the object ids will all be reset).

const log = console.log;
function* generateId() {
for(let i = 0; ; ++i) {
yield i;
}
}
const idGenerator = generateId();
const ObjectWithId = new Proxy(Object, {
construct(target, args) {
const instance = Reflect.construct(target, args);
instance['id'] = idGenerator.next().value;
return instance;
}
})
const myObject = new ObjectWithId({
name: '##NativeObject'
});
log(myObject.id);