err-object

Custom error object.

• supports to define error codes and messages in advance before use.
• provides cleaned error stack and we can manage the stack sanitizer by using error-stack (since 5.1.0)

Why

Tired writing code like this:

const error = new SomeError('message')
error.code = 'SOME_ERROR'

There are tremendous modules about custom errors in the NPM, but NONE of those is usable.

Install

$ npm i err-object

Usage

import {error} from 'err-object'
const message = 'message'

error(message)
// Error
// - message

error({
  message,
  name: 'ImplementError',
  code: 'ERR_IMPL'
})
// Error
// - message
// - name: 'ImplementError'
// - code: 'ERR_IMPL'

error(message, TypeError)
// TypeError
// - message

Creates error templates to manage multiple error types

We could use this to standardize the error objects of the whole project.

import {
  Errors,
  error as _error
} from 'err-object'
import util from 'util'

const {E, error, i18n} = new Errors()

// Error code, and message
E('ERR_NO_PERMISSION', 'you do not have permission to do this')

E('ERR_INVALID_TYPE', 'number expected but got %s', TypeError)
// Which is equivalent to:

// Error code
E('ERR_INVALID_TYPE', {
  // Custom error type
  ctor: TypeError,
  // Message template which will be formatted by `util.format`
  message: 'number expected but got %s'
})

// The equivalent default factory
const factory = ({code, preset, args, _}) => {
  const {
    ctor = Error,
    message: messageTemplate,
    ...others
  } = preset

  const message = util.format(_(messageTemplate), ...args)
  return _error({
    ...others,
    code,
    message,
    args
  }, Error)
}

E('ERR_INVALID_TYPE_2', {
  // Custom error type
  ctor: TypeError,
  // Message template which will be formatted by `util.format`
  message: 'number expected but got %s'

// We can define our custom error factory,
// and the default error factory is:
}, factory)

error('ERR_NO_PERMISSION')
// Error
// - code: 'ERR_NO_PERMISSION'
// - message: 'you do not have permission to do this'

error('ERR_INVALID_TYPE', 'string')
// TypeError
// - code: 'ERR_INVALID_TYPE'
// - message: 'number expected but got string'
// - args: ['string']

error('ERR_INVALID_TYPE_2', 'string')
// The same return value of the last statement

// The constructor `Errors` accepts a `options.factory` parameter,
// to define the default error factory.
// And so the following statement is equivalent to `new Errors()`
new Errors({
  factory
})

const ZH_CN_MAP = {
  'number expected but got %s': '期望 number 类型但实际为 %s'
}

i18n(message => ZH_CN_MAP[message] || message)

error('ERR_INVALID_TYPE', 'string')
// TypeError
// - code: 'ERR_INVALID_TYPE'
// - message: '期望 number 类型但实际为 string'
// - args: ['string']

error(thing, ctor)

• thing String|Object
• ctor Class=Error

new Errors(options)

• options? Object
  • factory? Function(code, preset, ...args) the default error factory (the default value please see above)
  • notDefined? Function(code, ...args)=exitOnNotDefined will create the error object if the given code is not defined by error.E. Since 5.0.0, if the given error code is not defined by error.E, it will throw an error and exit the current process.
  • ~~prefix? string~~ Deprecated in 4.4.0
  • messagePrefix? string the message prefix for every error message. New in 4.4.0
  • codePrefix? string the code prefix. New in 4.4.0
  • filterStackSources? Array<path>=[] defines source paths to be filtered out from error stacks. New in 5.1.0

error.E(code, preset, factory)

error.E(code, template, ctor)

Define an error preset.

• code string define the error code
• preset ?Object
  • ctor ?Error=Error the constructor of the error
  • template ?(string | Function(...args)) the message template which will be formatted by util.format()
  • other property/properties that you want to add to the error object.
• factory ?Function({code, preset, args, _}) the error factory
  • _ ?Function=(x=>x) the i18nConverter function which defaults to the function that just returns the argument.

Returns this

error.TE(code, template)

new in 4.5.0

Define a TypeError, in favor of using new TypeError('should be ..., but got something')

const {error, TE} = new Errors()

TE('INVALID_OPTIONS', 'options must be an object')

throw error('INVALID_OPTIONS', undefined)
// TypeError: options must be an object, but got `undefined`

error.i18n(i18nConverter)

• i18nConverter Function(string): string

Specify the i18n mapping function which receives the message template and returns the converted message template.

Returns this

error.error(code, ...args)

Creates a standard error object by code.

• code
• args Array<any> which will be passed and spreaded into factory after the code and the preset parameters.

Returns Error And if a given code is not defined by error.E(), the return value will be notDefined(code, ...args)

message prefix

const {E, error} = new Errors({
  messagePrefix: '[err-object] ',
  codePrefix: 'CORE_'
})

E('FATAL_ERROR', 'this is a fatal error')

const err = error('FATAL_ERROR')

console.log(err.message)
// [err-object] this is a fatal error
// - code: 'CORE_FATAL_ERROR'

options.filterStackSources

/path/to/a.js (before):

const {error, E} = new Error()
E('FOO', 'bar')
module.exports = code => error(code)

/path/to/b.js

const error = require('./a')
const err = error('FOO')

console.log(err.stack)
// Error: bar
//     at Object.<anonymous> (/path/to/a.js:3:1)
//     at error (/path/to/b.js:2:13)
//     ...

Let's take a look at the error stack above, the /path/to/a.js line is actually useless.

Then how to get rid of the first stack trace line? We can use options.filterStackSources

/path/to/a.js (after):

const {error, E} = new Error({
  filterStackSources: [
    // Filter out the current source file
    __filename
  ]
})
E('FOO', 'bar')
module.exports = code => error(code)

Then,

console.log(err.stack)
// Error: bar
//     at error (/path/to/b.js:2:13)
//     ...

License

MIT