So the real magic is here:

return {
name : config.name,
age : config.age,

get : function() {
return getPrivateValue(); },
set : function(newValue) { setPrivateValue(newValue); }
};

Not in the var…. above.

Doh! thanks!!

var David = Person({
    name : 'David',
    age  : 30,
    SSN  : '123-456-7890'
});

You can never DIRECTLY access David’s SSN property. It has a get/set method, which can modify the encapsulated variable (SSN, inside the function scope). SSN is never exposed outside the scope of the Person “factory” method.

I figured that was the case. In all then would you say exposing
var SSN = config.SSN;
thereby making it publicly accessible is confusing in an example which deals with encapsulation, especially given your example was the SSN variable.

Because Im not a Javascript guru, I was left scratching my head about it was that you ended up hiding SSN. The answer was that SSN was exposed and therefore not encapsulated.

Again, thanks for explaining (I hope Im right!! :-/ )

var David = Person({
    name : 'David',
    age  : 30,
    SSN  : '123-456-7890'
});

However, you can later call:

David.set('111-22-3333');

…which should hit your breakpoint.

One little point. I see that in your sample, your are subscribing and unsubscribing upon the destroy on the component. Instead of using ‘on’ and ‘un’, couldn’t you use just ‘mon’ ? (it will simplify you code even further…)

My .02 cents.

SSN : ’123-456-7890′

invokes

set : function(newValue) { setPrivateValue(newValue); }

I ran your code in chrome and put a break point on the set: function. The code did not stop at the breakpoint. Im new to Javascript.

getPrivateValue() is invoked whenever someone calls the method Person.get()… the same idea with setPrivateValue() and Person.set().

In short, getPrivateValue() and setPrivateValue() are private methods. They can never directly be called by anything because they are ENCAPSULATED within the closure. Person.get() invokes getPrivateValue() for us, but we can’t call it directly because of the private scope. Make sense?

The Person constructor returns an object literal. That object alone has access to the variables/methods contained within the closure.

SSN is assigned to a local variable (within the closure), so the only way to get/set it’s value is by calling getPrivateValue() and setPrivateValue(). If you were to override the Person.get() or Person.set() methods, we would lose our link to the data structures contained within the closure.

get : function() { return getPrivateValue(); },
set : function(newValue) { setPrivateValue(newValue); }

and how you are using:

function getPrivateValue() { return SSN; }
function setPrivateValue(value) { SSN = value; }

What is calling these methods??

SSN is assigned in the constructor, but I dont see what links it to those methods/functions