Pick any category of module and there's a good chance the most popular modules have little documentation; certainly nothing close to comprehensive.
I've never ran into the problem of feeling a module was poorly documented. The especially complex modules usually have more extensive documentation on their website. I'd say there are cases that are terrible or useful documentation for sure, but in general most modules are very good about it from my experience.
As said earlier, the core Node.js framework has great documentation, as do other frameworks such as Mongoose and Express.
Mongoose lacks a lot of documentation on the fringe use cases. However, the beauty of open source is that you can just read the code, which, in my experience, is the most reliable documentation.
The only requirement is for the application to print out in plain English if there is one of the following error:
* the document doesn't exist
* there is a connection error during download
* the local file couldn't be opened
* an error occured during writing.
For any other error(out of memory,...) the program can crash.
How do I do that in node? I don't know.
The request package only tells me the callback's first parameter is "An error when applicable (usually from http.ClientRequest object)". The fs package only tells me "Event: 'error': Emitted if there was an error when writing or piping data."
I only picked error reporting as an example so I could showcase the problem of lack of documentation on the most basic APIs (http get and writing file). By the way the Error Handling article [0] on Joyent's website is absolutely wonderful.
Call me old fashioned but how can I use an API that doesn't tell me which function to call, what a function accepts as parameters, what it returns or how it signals error?
The point of documentation is that you don't have to run the code to see what the code does.
https://github.com/mikeal/request
http://docs.python-requests.org/en/latest/
And 'request' is one of the better documented Node modules! Most authors don't bother with any documentation at all and take an 'if you're too dumb to read the source you shouldn't be using my package' attitude.
Of course there are exceptions, async is pretty nicely documented for example.
As to whether Node.js projects in general are better documented or worse than the average project in other languages... I dunno, that seems kind of anecdotal. Basic building blocks like `async`, `underscore`, `commander` etc. all have great documentation.