Node Custom Errors Examples

custom-errors.js

// REFERENCE: https://gist.github.com/slavafomin/b164e3e710a6fc9352c934b9073e7216

const generateMessage = (message, code, subcode) => {
  let errorCoding = '';
  if (code) errorCoding = `Code: ${code}`;
  if (subcode) errorCoding = `${errorCoding} Subcode: ${subcode}`;
  return `${message} ${errorCoding}`;
};

class CustomError extends Error {
  constructor(message, code, subcode) {
    // Calling parent constructor of base Error class.
    super(generateMessage(message, code, subcode));

    // Saving class name in the property of our custom error as a shortcut.
    this.name = this.constructor.name;

    // Capturing stack trace, excluding constructor call from it.
    Error.captureStackTrace(this, this.constructor);

    // Additional custom properties you want.
    if (code) {
      this.code = code;
    }

    if (subcode) {
      this.subcode = subcode;
    }
  }
}

class MailchimpError extends CustomError {
  constructor(message, code, subcode) {
    const defaultMessage = 'Unknown MailChimp Error';
    const defaultCode = 400;
    const defaultSubcode = 500;
    super((message || defaultMessage), (code || defaultCode), (subcode || defaultSubcode));
    this.feature = 'mailchimp';
    this.team = 'integration';
    this.helpDocLink = 'https://help.example.com/help-article';
  }
}

/**
 * This is an example of the base error handler
 */
try {
  throw new CustomError('It went bad!', 1234, 5678);
} catch (err) {
  if (err instanceof CustomError) {
    console.log('Custom error occurred!', err);
  } else {
    console.log('Unknown error', err);
  }
}

/**
 * Here's an example of how you can use the base error handler to add "service specific" or "feature level" logging
 */
try {
  throw new MailchimpError('Chimps died!');
} catch (err) {
  if (err instanceof MailchimpError) {
    console.log('MailChimp error occurred!', err);
  } else {
    console.log('Unknown error', err);
  }
}

Example output:

Runkit Example:
https://runkit.com/rveitch/5f625431d59540001ab3bef5

Priority level can also be added. Team and Feature are probably not necessary and bad long term as those can change but it's just an example.