A small utility, used by Fastify itself, for generating consistent error objects across your codebase and plugins.

npm i @fastify/error

The module exports a function that you can use for consistent error objects, it takes 4 parameters:

createError(code, message [, statusCode [, Base]])

• code (string, required) - The error code, you can access it later with error.code. For consistency, we recommend prefixing plugin error codes with FST_
• message (string, required) - The error message. You can also use interpolated strings for formatting the message.
• statusCode (number, optional) - The status code that Fastify will use if the error is sent via HTTP.
• Base (ErrorConstructor, optional) - The base error object that will be used. (eg TypeError, RangeError)

const createError = require('@fastify/error')
const CustomError = createError('ERROR_CODE', 'Hello')
console.log(new CustomError()) // error.message => 'Hello'

How to use an interpolated string:

const createError = require('@fastify/error')
const CustomError = createError('ERROR_CODE', 'Hello %s')
console.log(new CustomError('world')) // error.message => 'Hello world'

How to add cause:

const createError = require('@fastify/error')
const CustomError = createError('ERROR_CODE', 'Hello %s')
console.log(new CustomError('world', {cause: new Error('cause')})) 
// error.message => 'Hello world'
// error.cause => Error('cause')

It is possible to limit your error constructor with a generic type using TypeScript:

const CustomError = createError<[string]>('ERROR_CODE', 'Hello %s')
new CustomError('world')
//@ts-expect-error
new CustomError(1)

Licensed under MIT.