Usually I would be against simulating language features which aren't part of the language in the first place. JavaScript is kind of different, though.

On the web, many developers are "forced" to write JavaScript when they don't really understand it (which is a massive pet peeve of mine, but that's a rant for another time). These developers tend to try and shoehorn design patterns from their language of choice into JS, or they just don't use any design patterns at all. Either way, it just doesn't work; the code just ends up being horrible.

At least libraries like this allow people to use design patterns that are more familiar to them, which should (hopefully) result in cleaner code.