It's also very short. A total breath of fresh air in an industry where so many publishers have a "bigger is better" mentality.
I wish there was a single curriculum that most JS developers were exposed to and can point to.
Every JS developer I meet has a different way of doing encapsulation and abstraction. This makes it terribly confusing for developers new to the environment who just want to know "the typical way" you do XYZ.
The second major problem with Javascript is that it was prematurely standardized due to excessive pressure to ship during development, and thus has a lot of little mis-features and defects in the core language that haven't been fixed due to concerns about breaking backward compatibility. Luckily it's generally possible to avoid these areas of the language without having to compromise your code so it's just a matter of keeping to good practices and of knowing what to avoid.
The third problem is that Javascript is primarily a web technology where it is married to the DOM, and historically browser DOMs have been a mess: non-standardized, buggy, sometimes slow.
Overall the result is a language with a few landmines that need to be tiptoed around but that is still very solid in its fundamentals. Compare that with many other languages that are more polished and yet fundamentally limited in significant ways (such as Java's lack of closures, for example).
The wonderful thing about JS is that because of its expressiveness, power, and advanced featureset, using the language properly becomes a potent self-reinforcing feedback loop, jQuery is one of the better examples of this.
http://openjsan.org/doc/s/sa/samuraijack/Joose/3.011/lib/Joo...
It's like a tasteful mix of Python and Javascript, but without any of the fat. It's very dynamic, has a small, extremely portable, and high-performance implementation (in a ~200k C library), has prototype-based objects, a JSON-like native datatype, and a better JIT (http://luajit.org/) than any JS implementation thus far.
Recommended introduction: Ierusalimschy's _Programming in Lua, 2nd ed._ (http://www.inf.puc-rio.br/~roberto/pil2/).