@alessiofrittoli/exception

Exception 🚦

Handle errors with ease

This documentation describes the Exception class, which provides a structured way to handle errors in TypeScript. It includes custom properties such as code, name, and status for more detailed error reporting and debugging.

Table of Contents

• Getting started
• API Reference
  • ExceptionOptions Interface
  • Exception Class
  • AbortError Class
    • AbortError Usage Scenarios
  • ErrorCode enum
  • Examples
• Development
  • Install depenendencies
  • Build the source code
  • ESLint
  • Jest
• Contributing
• Security
• Credits

Overview

The Exception class extends the native JavaScript Error object, adding customizable fields to improve error classification and handling. It also includes a static utility method to check if an object is an instance of the Exception class.

Getting started

Run the following command to start using @alessiofrittoli/exception in your projects:

npm i @alessiofrittoli/exception

or using pnpm

pnpm i @alessiofrittoli/exception

API Reference

ExceptionOptions Interface

The ExceptionOptions interface defines the optional parameters for the Exception class constructor.

Properties

Property	Type	Default	Description
code	TCode	-	(Required) A numeric or custom code representing the error type.
name	string	Exception	(Optional) A string representing the error name.
status	number	-	(Optional) An HTTP status code associated with the error.

Exception Class

The Exception class extends the Error object and implements the ExceptionOptions interface.

Constructor

The constructor initializes an Exception instance with a custom message and options.

Parameters

Parameter	Type	Description
message	TMessage	(Required) The error message. Can be a string or a custom type.
options	ExceptionOptions	(Required) An object containing the error options.

Example

import { Exception } from '@alessiofrittoli/exception'

try {
  throw new Exception( 'Resource not found', {
    code    : 'ERR:NOTFOUND',
    status  : 404,
  } )
} catch ( error ) {
  console.error( error )
}

Static Methods

isException

A utility method to check if an object is an instance of the Exception class.

It supports also a JSON representation of the Exception class (commonly returned by server responses).

Example

try {
  throw new Exception( 'Something went wrong', { code: 'ERR:UNKNOWN' } )
} catch ( error ) {
  if ( Exception.isException( error ) ) {
    // we can safely access `Exception` properties
    console.error( `Error [${ error.code }]: ${ error.message }` )
  } else {
    console.error( error )
  }
}

/** Simulates JSON Exception returned by a server JSON Response. */
const error = (
  JSON.parse( JSON.stringify( new Exception( 'Exception with custom name.', {
    code: 0,
    name: 'AbortError',
  } ) ) )
)

console.log( Exception.isException( error ) ) // Outputs: true

AbortError Class

The AbortError class extends the Exception Class and offers a preset configuration for easier usage.

Constructor

The constructor initializes an AbortError instance with a custom message and options.

Parameters

Parameter	Type	Description
message	TMessage	(Required) The error message. Can be a string or a custom type.
options	AbortErrorOptions	(Optional) An object containing the error options. It extends the ExceptionOptions Interface and omit the name property. The code defaults to ErrorCode.ABORT but can be optionally customized.

AbortError Usage Scenarios

Precise Abort Errors Handling

import { AbortError } from '@alessiofrittoli/exception/abort'

try {
  const controller = new AbortController()
  const { signal } = controller

  button.addEventListener( 'click', () => {
    controller.abort( new AbortError( 'User cancelled the request.' ) )
  } )

  await fetch( ..., { signal } )
} catch ( error ) {

  if ( AbortError.isException( error ) ) {
    if ( AbortError.isAbortError( error ) ) {
      // handle abort error
      console.log( error.code ) // `error.code` is type of `ErrorCode.ABORT`.
      return
    }
    // handle other Exception errors
    return
  }
  // handle other unknown errors
  
}

Using custom Abort Error codes

import { AbortError } from '@alessiofrittoli/exception/abort'

enum CustomAbortCode
{
  CUSTOM_CODE = 'ERR:CUSTOM_ABORT_CODE',
}

try {
  const controller = new AbortController()
  const { signal } = controller

  button.addEventListener( 'click', () => {
    controller.abort(
      new AbortError( 'User cancelled the request.', { code: CustomAbortCode.CUSTOM_CODE } )
    )
  } )

  await fetch( ..., { signal } )
} catch ( error ) {

  if ( AbortError.isException( error ) ) {
    if ( AbortError.isAbortError( error, CustomAbortCode.CUSTOM_CODE ) ) {
      // handle abort error
      console.log( error.code ) // `error.code` is type of `CustomAbortCode.CUSTOM_CODE`.
      return
    }
    // handle other Exception errors
    return
  }
  // handle other unknown errors
  
}

ErrorCode enum

The ErrorCode enum is a utility that provides pre-defined constants for the most common error codes.
It is designed to simplify error handling and improve feedback quality returned to the user.

Constants Overview

Constant	Value	Description
UNKNOWN	ERR:UNKNOWN	Returned when an unexpected error occured.
ABORT	ERR:ABORT	Returned when user abort the request.
EMPTY_VALUE	ERR:EMPTYVALUE	Returned when a required value is "falsy".
WRONG_VALUE	ERR:WRONGVALUE	Return when a required value is not the expected value.
EXPIRED	ERR:EXPIRED	Returned when a requested has been performed too late.
TOO_EARLY	ERR:TOOEARLY	Returned when a request has been performed too early.
TOO_MANY	ERR:TOOMANY	Could be return in combination with a 429 Too Many Requests Response Status.
QUOTA_REACHED	ERR:QUOTAREACHED	Returned when a specific quota has been reached.
NOT_FOUND	ERR:NOTFOUND	Returned when a resource cannot be found.
OFFLINE	ERR:INTERNETDISCONNECTED	Could be used to throw errors when user is offline.

Extending the `enum` in your project

For obvious reasons the default ErrorCode provided by this library might be not enough to cover all the error cases in your project.

To fill this gap, you can "extend" the ErrorCode enum by doing so:

// myproject/src/error-code.ts
import { ErrorCode as Exception } from '@alessiofrittoli/exception/code'

/** Your project custom `ErrorCode`. */
export enum MyProjectErrorCode
{
  INVALID_SIGN = 'ERR:INVALIDSIGN',
}

const ErrorCode = { Exception, MyProjectErrorCode }
type ErrorCode = MergedEnumValue<typeof ErrorCode>

export default ErrorCode

⚠️ The Type MergedEnumValue<T> is globally delcared from @alessiofrittoli/type-utils so make sure to install it if needed.

Examples

Using the default ErrorCode to throw a new Exception

import { Exception } from '@alessiofrittoli/exception'
import { ErrorCode } from '@alessiofrittoli/exception/code'

throw new Exception( 'Password is a required field to log you in.', {
  code    : ErrorCode.EMPTY_VALUE,
  status  : 422,
} )

Using custom ErrorCode to throw a new Exception

import { Exception } from '@alessiofrittoli/exception'
import { ErrorCode } from '@/error-code' // previously created in `myproject/src/error-code.ts`

throw new Exception( 'Invalid signature.', {
  code    : ErrorCode.MyProjectErrorCode.INVALID_SIGN,
  status  : 403,
} )

Using ErrorCode to handle errors

import { ErrorCode } from '@/error-code' // previously created in `myproject/src/error-code.ts`

try {
  ...
} catch ( error ) {
  if ( Exception.isException<string, ErrorCode>( error ) ) {
    switch ( error.code ) { // `error.code` is now type of `ErrorCode` (custom).
      case ErrorCode.MyProjectErrorCode.INVALID_SIGN:
        console.log( 'The signature is not valid.' )
        break
      case ErrorCode.Exception.UNKNOWN:
      default:
        console.log( 'Unexpected error occured.' )
    }
  }
}

Development

Install depenendencies

npm install

or using pnpm

pnpm i

Build the source code

Run the following command to test and build code for distribution.

pnpm build

ESLint

warnings / errors check.

pnpm lint

Jest

Run all the defined test suites by running the following:

# Run tests and watch file changes.
pnpm test:watch

# Run tests in a CI environment.
pnpm test:ci

• See package.json file scripts for more info.

Run tests with coverage.

An HTTP server is then started to serve coverage files from ./coverage folder.

⚠️ You may see a blank page the first time you run this command. Simply refresh the browser to see the updates.

test:coverage:serve

Contributing

Contributions are truly welcome!

Please refer to the Contributing Doc for more information on how to start contributing to this project.

Help keep this project up to date with GitHub Sponsor.

Security

If you believe you have found a security vulnerability, we encourage you to responsibly disclose this and NOT open a public issue. We will investigate all legitimate reports. Email [e-mail] to disclose any security vulnerabilities.

Made with ☕

Alessio Frittoli https://alessiofrittoli.it | [e-mail]