doc: errno is a number, not a string

[jvilk]

Checklist

• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

doc

Description of change

The documentation erroneously described the errno property as an alias for the
code property, but that is not the case in the implementation. errno is the
error code of the error as a number, and code is the error code of the error
as a string.

As proof, here's some code:

fs.readFile("nonexistantdjkfald", function(e) {
  console.log(e.errno); 
  console.log(typeof(e.errno));
  console.log(e.code);
  console.log(typeof(e.code));
});

Output:

-2
number
ENOENT
string

[jvilk]

Note: Since this documentation change is relevant to currently released versions of Node, it should probably be backported to relevant branches.

[lpinca]

LGTM

[gibfahn]

Maybe Returns a number corresponding to an error code ? LGTM either way.

[gibfahn]

Also it's a small thing, but if you could wrap your commit message at 72 chars that'd be great.

[jvilk]

@gibfahn I have clarified the documentation, and fixed the commit message. Please note that I have added extra information since the last commit. Node negates the error code, so an error code of 2 becomes -2. I hope the new text is understandable; if not, I am open to editing suggestions! :)

[lpinca]

Landed in f478b46.
Thank you!