Trying to understand nodejs documentation. How to discover callback parameters

Question

When I read this Node.js API docs, it raises a few questions for me.

1. In this particular case, is the example they use the only thing that tells me that the 1 parameter in the callback is 'err'?
2. Going forward do I assume that there is only the 'err' parameter in the callback unless otherwise noted?
3. Seems to me to me the callback parameters should be listed in a common pattern, like here: "callback <Function>" in the header. Why am I wrong in that thinking?

Answer 1

Documentation on fs:

The asynchronous form always takes a completion callback as its last argument. The arguments passed to the completion callback depend on the method, but the first argument is always reserved for an exception. If the operation was completed successfully, then the first argument will be null or undefined.

So, yes, assume callback to fs methods to have signature (err) unless noted otherwise. You should not assume this to be the signature of other packages, unless it is noted similarly.

Is there a standard doc producing tool like javadoc in javascript?

What options are available for documenting your Javascript code?