Mozilla online documentation are great, but sometimes I don't have the internet connection and reference in the o'reilly javascript definitive guide is also great but lack of the handy searchable capability.
I just wonder if there anything for javascript like railsapi, or yard, or jQAPI
You can probably blame the lack of uniform documentation styles and the fact that there is no centrally approved Javascript "stdlib", but there seems to be no such off-line doc generators or generated documentation.
There is, strangely, a certain amount of documentation available as Windows help files (CHM):