n-custom-errors

Custom errors for Node.js.

Features

• custom errors with name, code and error message.
• template strings for formatting error messages.
• helper functions for each registered error:
  • get<errorName>Error()
  • get<errorName>ErrorType()
  • is<errorName>Error()

Setting up

# Add to project
$ npm i n-custom-errors

Usage

// Registering errors:
customErrors.registerError('AccessDenied', 403);
customErrors.registerError('DuplicateObject', 409);
customErrors.registerError('ObjectNotFound', 404, '${objectName} not found');

// Creating custom errors:
let objectNotFoundError = customErrors.getObjectNotFoundError({ objectName: 'user' });
let duplicateObjectError = customErrors.getDuplicateObjectError('The email is not unique');

console.log(objectNotFoundError);
/*
prints => {
  name: 'ObjectNotFoundError',
  message: 'user not found',
  statusCode: 404
}*/
console.log(duplicateObjectError);
/*
prints => {
  name: 'DuplicateObjectError',
  message: 'The email is not unique',
  statusCode: 409
}*/

// Checking that an error is a custom error:
let err = new Error();
let objectNotFoundError = customErrors.getObjectNotFoundError({ objectName: 'user' });
customErrors.isObjectNotFoundError(err)); // returns false
customErrors.isObjectNotFoundError(objectNotFoundError)); // returns true

API

• registerError(name, statusCode, messageTemplate)
  Registers a new custom error.

  • name - error name, required, must be an unique. Name must be without Error postfix.
  • statusCode - http status code for error.
  • messageTemplate - template for a message, must contains parameters in the following format: ${objectName} not found. To pass the parameters to the template, parameters must be an object with defined properties: customErrors.getObjectNotFoundError({ objectName: 'user' }). If parameters is a string, than this string will be used in an error message without template: customErrors.getObjectNotFoundError('User with a name user1 not found, please use another filter').

• isKnownError(err)
  Returns true if err is a registered custom error, false otherwise.

  • err - error object, required.

• get<errorName>Error(msg)
  This function is added automatically when a new custom error is registered.
  Creates a custom error with message msg, it can be the parameters object if an error is registered with messageTemplate.

  • msg - an error message, required.

• get<errorName>ErrorType()
  This function is added automatically when a new custom error is registered.
  Gets a custom error type.

• is<errorName>Error(err)
  This function is added automatically when a new custom error is registered.
  Returns true if err is a custom error, false otherwise.

  • err - error object, required.

Author

Alexander Mac

License

Licensed under the MIT license.