Huge News!Announcing our $40M Series B led by Abstract Ventures.Learn More
Socket
Sign inDemoInstall
Socket

new-error

Package Overview
Dependencies
Maintainers
2
Versions
46
Alerts
File Explorer

Advanced tools

Socket logo

Install Socket

Detect and block malicious and high-risk dependencies

Install

new-error

A production-grade error creation and serialization library designed for Typescript

  • 1.0.5
  • Source
  • npm
  • Socket score

Version published
Weekly downloads
87
decreased by-40.41%
Maintainers
2
Weekly downloads
 
Created
Source

new-error

NPM version CircleCI built with typescript JavaScript Style Guide

A production-grade error creation library designed for Typescript. Useful for direct printing of errors to a client or for internal development / logs.

  • All created errors extend Error with additional methods added on.
  • Show errors that are safe for client / user-consumption vs internal only.
  • Create your own custom error types with custom messaging, status codes and metadata.
  • Attach an error to your error object to get the full error chain.
  • Selectively expose error metadata based on internal or external use.
  • Built-in auto-completion for Typescript when searching for registered error types.
  • 100% test coverage

Generating an error with autocompletion

Table of Contents

Installation

$ npm i new-error --save

Example Usage

  • Define a set of high level errors
    • Common high level error types could be 4xx/5xx HTTP codes
  • Define a set of low level errors
    • Think of low level errors as a fine-grained sub-code/category to a high level error
  • Initialize the error registry with the errors
// This is a working example
import { ErrorRegistry } from 'new-error'

// Define high level errors
// Do *not* assign a Typescript type to the object
// or IDE autocompletion will not work!
const errors = {
  INTERNAL_SERVER_ERROR: {
   /**
    * The class name of the generated error
    */
    className: 'InternalServerError',
    /**
     * A user-friendly code to show to a client.
     */
    code: 'ERR_INT_500',
   /**
    * (optional) Protocol-specific status code, such as an HTTP status code. Used as the
    * default if a Low Level Error status code is not specified or defined.
    */
    statusCode: 500
  }
}

// Define low-level errors
// Do *not* assign a Typescript type to the object
// or IDE autocompletion will not work!
const errorCodes = {
  // 'type' of error
  DATABASE_FAILURE: {
    /**
     * Full description of the error. sprintf() flags can be applied
     * to customize it.
     * @see https://www.npmjs.com/package/sprintf-js
     */
    message: 'There was a database failure, SQL err code %s',
    /**
     * (optional) A user-friendly code to show to a client.
     */
    subCode: 'DB_0001',
    /**
     * (optional) Protocol-specific status code, such as an HTTP status code.
     */
    statusCode: 500
  }
}

// Create the error registry by registering your errors and codes
// you will want to memoize this as you will be using the
// reference throughout your application
const errRegistry = new ErrorRegistry(errors, errorCodes)

// Create an instance of InternalServerError
// Typescript autocomplete should show the available definitions as you type the error names
// and type check will ensure that the values are valid
const err = errRegistry.newError('INTERNAL_SERVER_ERROR', 'DATABASE_FAILURE').formatMessage('SQL_1234')
console.log(err.toJSON())

Produces:

(You can omit fields you do not need - see usage section below.)

{
  name: 'InternalServerError',
  code: 'ERR_INT_500',
  message: 'There was a database failure, SQL err code SQL_1234',
  type: 'DATABASE_FAILURE',
  subCode: 'DB_0001',
  statusCode: 500,
  meta: {},
  stack: 'InternalServerError: There was a database failure, SQL err code %s\n' +
    '    at ErrorRegistry.newError (new-error/src/ErrorRegistry.ts:128:12)\n' +
    '    at Object.<anonymous> (new-error/src/test.ts:55:25)\n' +
    '    at Module._compile (internal/modules/cjs/loader.js:1158:30)\n' +
    '    at Module._compile (new-error/node_modules/source-map-support/source-map-support.js:541:25)\n' +
    '    at Module.m._compile (/private/var/folders/mx/b54hc2lj3fbfsndkv4xmz8d80000gn/T/ts-node-dev-hook-20649714243977457.js:57:25)\n' +
    '    at Module._extensions..js (internal/modules/cjs/loader.js:1178:10)\n' +
    '    at require.extensions.<computed> (/private/var/folders/mx/b54hc2lj3fbfsndkv4xmz8d80000gn/T/ts-node-dev-hook-20649714243977457.js:59:14)\n' +
    '    at Object.nodeDevHook [as .ts] (new-error/node_modules/ts-node-dev/lib/hook.js:61:7)\n' +
    '    at Module.load (internal/modules/cjs/loader.js:1002:32)\n' +
    '    at Function.Module._load (internal/modules/cjs/loader.js:901:14)'
}

Error Registry

The ErrorRegistry is responsible for the registration and creation of errors.

Creating errors

Errors generated by the registry extends BaseError.

Create a well-defined error

Method: ErrorRegistry#newError(highLevelErrorName, LowLevelErrorName)

This is the method you should generally use as you are forced to use your well-defined high and low level error definitions. This allows for consistency in how errors are defined and thrown.

// Creates an InternalServerError error with a DATABASE_FAILURE code and corresponding
// message and status code
const err = errRegistry.newError('INTERNAL_SERVER_ERROR', 'DATABASE_FAILURE')

Create an error without a low-level error

Method: ErrorRegistry#newBareError(highLevelErrorName, message)

This method does not include a low level error code, and allows direct specification of an error message.

// Creates an InternalServerError error with a custom message
const err = errRegistry.newBareError('INTERNAL_SERVER_ERROR', 'An internal server error has occured.')

instanceOf / comparisons

Comparing a custom error

Method: ErrorRegistry#instanceOf(classInstance, highLevelErrorName)

Performs an instanceof operation against a custom error.

// creates an InternalServerError error instance
const err = errRegistry.newError('INTERNAL_SERVER_ERROR', 'DATABASE_FAILURE')

if (errRegistry.instanceOf(err, 'INTERNAL_SERVER_ERROR')) {
  // resolves to true since err is an InternalServerError instance
}

Native instanceof

You can also check if the error is custom-built using this check:

import { BaseError } from 'new-error'

function handleError(err) {
  if (err instanceof BaseError) {
    // err is a custom error
  }
}

Error API

Except for the serialization methods, all methods are chainable.

Generated errors extend the BaseError class, which supplies the manipulation methods.

Getters

  • BaseError#getCode()
  • BaseError#getSubCode()
  • BaseError#getStatusCode()
  • BaseError#getCausedBy()
  • BaseError#getMetadata()
  • BaseError#getSafeMetadata()

Attaching errors

Method: BaseError#causedBy(err)

You can attach another error to the error.

const externalError = new Error('Some thrown error')
err.causedBy(externalError)

Format messages

Method: BaseError#formatMessage(...formatParams)

See the sprintf-js package for usage.

// specify the database specific error code
// Transforms the message to:
// 'There was a database failure, SQL err code %s' ->
// 'There was a database failure, SQL err code SQL_ERR_1234',
err.formatMessage('SQL_ERR_1234')

Adding metadata

Safe metadata

Method: BaseError#withSafeMetadata(data = {})

Safe metadata would be any kind of data that you would be ok with exposing to a client, like an HTTP response.

err.withSafeMetadata({
  errorId: 'err-12345',
  moreData: 1234
})
// can be chained to append more data
.withSafeMetadata({
  requestId: 'req-12345'
})

This can also be written as:

err.withSafeMetadata({
  errorId: 'err-12345',
  moreData: 1234
})

// This will append requestId to the metadata
err.withSafeMetadata({
  requestId: 'req-12345'
})

Internal metadata

Method: BaseError#withMetadata(data = {})

Internal metadata would be any kind of data that you would not be ok with exposing to a client, but would be useful for internal development / logging purposes.

err.withMetadata({
  email: 'test@test.com'
})
// can be chained to append more data
.withMetadata({
  userId: 'user-abcd'
})

Serializing errors

Safe serialization

Method: BaseError#toJSONSafe(fieldsToOmit = [])

Generates output that would be safe for client consumption.

  • Omits name
  • Omits message
  • Omits causedBy
  • Omits type
  • Omits the stack trace
  • Omits any data defined via BaseError#withMetadata()
err.withSafeMetadata({
  errorId: 'err-12345',
  requestId: 'req-12345'
})
// you can remove additional fields by specifying property names in an array
//.toJSONSafe(['code']) removes the code field from output
.toJSONSafe()

Produces:

{
  code: 'ERR_INT_500',
  subCode: 'DB_0001',
  statusCode: 500,
  meta: { errorId: 'err-12345', requestId: 'req-12345' }
}

Internal serialization

Method: BaseError#toJSON(fieldsToOmit = [])

Generates output that would be suitable for internal use.

  • Includes name
  • Includes type
  • Includes message
  • Includes causedBy
  • Includes the stack trace
  • All data from BaseError#withMetadata() and BaseError#withJSONMetadata() is included
err.withSafeMetadata({
  errorId: 'err-12345',
}).withMetadata({
  email: 'test@test.com'
})
// you can remove additional fields by specifying property names in an array
//.toJSON(['code', 'statusCode']) removes the code and statusCode field from output
.toJSON()

Produces:

{
  name: 'InternalServerError',
  code: 'ERR_INT_500',
  message: 'There was a database failure, SQL err code %s',
  type: 'DATABASE_FAILURE',
  subCode: 'DB_0001',
  statusCode: 500,
  meta: { errorId: 'err-12345', requestId: 'req-12345' },
  stack: 'InternalServerError: There was a database failure, SQL err code %s\n' +
    '    at ErrorRegistry.newError (new-error/src/ErrorRegistry.ts:128:12)\n' +
    '    at Object.<anonymous> (new-error/src/test.ts:55:25)\n' +
    '    at Module._compile (internal/modules/cjs/loader.js:1158:30)\n' +
    '    at Module._compile (new-error/node_modules/source-map-support/source-map-support.js:541:25)\n' +
    '    at Module.m._compile (/private/var/folders/mx/b54hc2lj3fbfsndkv4xmz8d80000gn/T/ts-node-dev-hook-17091160954051898.js:57:25)\n' +
    '    at Module._extensions..js (internal/modules/cjs/loader.js:1178:10)\n' +
    '    at require.extensions.<computed> (/private/var/folders/mx/b54hc2lj3fbfsndkv4xmz8d80000gn/T/ts-node-dev-hook-17091160954051898.js:59:14)\n' +
    '    at Object.nodeDevHook [as .ts] (new-error/node_modules/ts-node-dev/lib/hook.js:61:7)\n' +
    '    at Module.load (internal/modules/cjs/loader.js:1002:32)\n' +
    '    at Function.Module._load (internal/modules/cjs/loader.js:901:14)'
}

Example Express Error Handling

import express from 'express'
import { ErrorRegistry, BaseError } from 'new-error'
const app = express()
const port = 3000

const errors = {
  INTERNAL_SERVER_ERROR: {
    className: 'InternalServerError',
    code: 'ERR_INT_500',
    statusCode: 500
  }
}

const errorCodes = {
  DATABASE_FAILURE: {
    message: 'There was a database failure.',
    subCode: 'DB_0001',
    statusCode: 500
  }
}

const errRegistry = new ErrorRegistry(errors, errorCodes)

// middleware definition
app.get('/', async (req, res, next) => {
  try {
    // simulate a failure
    throw new Error('SQL issue')
  } catch (e) {
    const err = errRegistry.newError('INTERNAL_SERVER_ERROR', 'DATABASE_FAILURE')
    err.causedBy(err)
    // errors must be passed to next()
    // to be caught when using an async middleware
    return next(err)
  }
})

// catch errors
app.use((err, req, res, next) => {
  // error was sent from middleware
  if (err) {
    // check if the error is a generated one
    if (err instanceof BaseError) {
      // get the status code, if the status code is not defined, default to 500
      res.status(err.getStatusCode() ?? 500)
      // spit out the error to the client
      return res.json({
        err: err.toJSONSafe()
      })
    }
  }

  // no error, proceed
  next()
})

app.listen(port, () => console.log(`Example app listening at http://localhost:${port}`))

If you visit http://localhost:3000, you'll get a 500 status code, and the following response:

{"err": {"code":"ERR_INT_500","subCode":"DB_0001","statusCode":500,"meta":{}}}

Keywords

FAQs

Package last updated on 15 May 2020

Did you know?

Socket

Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.

Install

Related posts

SocketSocket SOC 2 Logo

Product

  • Package Alerts
  • Integrations
  • Docs
  • Pricing
  • FAQ
  • Roadmap
  • Changelog

Packages

npm

Stay in touch

Get open source security insights delivered straight into your inbox.


  • Terms
  • Privacy
  • Security

Made with ⚡️ by Socket Inc