[jhchen]

HTTP has standard error codes that tell you why a file didn't download (ex. 404 means it doesn't exist). File systems behave similarly (ex. ENOENT). None of this is language specific and therefore do not belong in Node.js documentation (except perhaps to say that these Node.js libraries also adhere to the same standards everyone else does but this is obvious the moment one of these error objects is printed or inspected).

[nawitus]

>but this is obvious the moment one of these error objects is printed or inspected

The point of documentation is that you don't have to run the code to see what the code does.