Question: Simple as that, can we emulate the "protected" visibility in Javascript somehow?

Answer: 
Do this:

```
/* Note: Do not break/touch this object */
...code...

```

Or a bit of google found this on the first page:

<http://blog.blanquera.com/2009/03/javascript-protected-methods-and.html>
What could that possibly mean? You don't have *classes*.

I suppose you could analyze `caller` to determine whether it meets some set of criteria for being permitted to call a method. This will be hideously inefficient and your criteria will always be spoofable.