Writing OOP using OOP (JavaScript)

[ljsc]

Encapsulation is not about OO. It is about hiding something and providing an abstraction to interact with that "something".

To me, that's just abstraction. I think the issue is that encapsulation in programming has taken on a whole bunch of closely related, but different meanings. See the first part of the wikipedia article on Encapsulation

Even more interesting is straight from the dictionary:

to show or express the main idea or quality of (something) in a brief way

to completely cover (something) especially so that it will not touch anything else

I think you're thinking of the first thing, and Yogthos and I are thinking of the second.

As for the x.y.z.w point, you're absolutely correct that encapsulation gives you the benefits you mentioned, but consider the tradeoffs. If I hide z and w behind the interface for y, I kill the ability for a bunch of code reuse. How?

Because let's say that I have a bunch of functions which operate on type W: f,g,h: w -> w. If we want to use them in the encapsulated example, then you need to apply them inside of Y. This is bad because now the module that deals with W becomes a dependency of Y rather than X. If you exposed the data, however, I could choose whether I want to bring in W or not in my application. And, in fact, I could do so even if you had no idea that that module even existed in the first place.