Why does Node.js specify error.code for Errors but response.statusCode for Response?

Question

I am getting myself confused between code and status working with Node.js and Express.

When I create an Error() I do this for example:

const Err = new Error();
Err.message = "Login failed";
Err.code = 401;   // why is this not Err.statusCode or Err.status ?
throw(Err);

Returning that via Express ends up becoming:

catch (error) {
return res.status(error.code).send(error.message);
}

The Express.js documentation says that res.status is an alias of Node's response.statusCode .

So why is the same code expressed in three different ways: error.code , response.statusCode and res.status . Why isn't it consistently the same?

Answer 1

Essentially the code and status you're talking about refer to two different concepts.

1 - The Error class code property refers to a standard node.js concept and is not http-specific - just like the Error class iteself.

This is what node's documentation says about it:

The error.code property is a string label that identifies the kind of error.

If you want an Error object representing a http error to actually hold a http status information, then nothing prevents you from adding a dedicated custom status - or statusCode - property. A httpError value for the code property would probably be more fitting in this case since it refers to a higher-level concept than a more fine-grained http status.

2 - response.statusCode and response.status on the other hand are both http specific and relate to the http status of a http.ServerResponse object. The http.ServerResponse class is defined by node.js, and res.status is just a shorthand setter that is added by express for conveniency - and couldn't possibly be named after the same name as the property it serves as a setter for.