Error.name vs Error.code

[stouf]

• Node.js Version: >=8.3.0
• OS: Any
• Scope (install, code, runtime, meta, other?): Best practice
• Module (and version) (if relevant): Errors

There seem to be an ongoing effort in node.js for getting any error thrown by the code functions to have a code property (see this pull request or this issue for example).

As a node.js user, I'm used to use the name property to programmatically identify errors in the code I write. For example,

// user.js
async function getByEmail(email) {
  const resultSet = await db.getBy('user', { email });
  if (resultSet.length === 0) {
    const error = new Error(`No user with the email ${email} could be found`);
    error.name = 'EMAIL_NOT_FOUND';
    throw error;
  }
  return resultSet;
}


// In some business logic code
user.getByEmail(inputEmail)
  .then((resultSet) => {
    return `Are you one of those? ${resultSet.map(x => x.name).join(',')}`;
  })
  .catch((error) => {
    if (error.name === 'EMAIL_NOT_FOUND') {
      return 'No user could be found for the input email';
    }
    throw error;
  });

Although the name property is not mentioned in Node.js documentation about Errors, it is a standard property and Node.js documentation about Errors tells us the following:

All JavaScript and System errors raised by Node.js inherit from, or are instances of, the standard JavaScript Error class and are guaranteed to provide at least the properties available on that class.

Now that the code is property is mentioned in Node.js documentation, I am wondering which of code and name I should use as a user for programmatically identifying errors.

Is there anything one should be aware of? Does the node.js team encourage for the use of one over the other?

[jasnell]

For core, especially given that we are still in the process of migrating errors, use code first, but if code is not present, use name

[jasnell]

Answer part 2 .... unfortunately many errors cannot be determined just by their name and require looking into the error message to understand what happened... which is why we're introducing code

[stouf]

Thanks for responding :)

I see. What about it for people building their own applications in Node.js and aiming at programmatically identifying the errors their own code creates? Would the node.js team encourage using code or name for that? Or maybe it's just up to the developers and there is no such thing as good practice for that?

[tniessen]

Our goal is to make the code property the optimal way to distinguish and identify errors.

aiming at programmatically identifying the errors their own code creates?

We are working on a good error handling strategy. There has already been a similar question at nodejs/node#15057 and the discussion is being continued in nodejs/CTC#173.

[stouf]

@tniessen Awesome, thanks for the reference 👍