I have usually found, installed and started using a good javascript library in less time than it would take me to make sense of MSDNs enterprise-soup documentation.
Whereas with C# or Java or Ruby or Python or countless other languages the standard library is big enough that a quick search, find an example and boom I'm done (I always thought the MSDN was amazing; it's like Mozilla's JS documentation but for C# with tons of awesome examples). If it's highly complex I can find a library that likely depends mostly on standard library functions and not have to worry about tons of dependencies.
I do a ton of development in JS and I think its standard library is one of its biggest flaws. ECMA would rather avoid adding too much to it as they seem to view the language as a small, scripting language and the platform should provide everything. That's a valid view, I think, but I don't agree with it at all. It's grown far too much to keep that view IMO.
I read C# documentation several times a week. I do not like it.
While I can't ever remember reading some documentation and saying, "Wow, that was fun!", so I can't say there's any documentation I like. But I do find that the MSDN documentation usually gets me working, and not reading documentation much faster than others for e.g. Python, Java, JavaScript, CSS, my pedometer.
MDN (Mozilla documentation for web stuff) is generally pretty good. Obnoxious colors aside, this javascript library is very easy to get started with: