This book is FANTASTIC to understand functors & monads.
Not sure it is a good resource to learn the Javascript language.
(but if you are beyond the beginner level, I highly recommend it, it really rocks!)
I think there is. The original author was consulting at the time it was written and he released the book right at ES6 took headwind. Another contributor has a fork and they are currently working to get the book up to date with ES6. Once that is done I am sure they will move on to part 5.