normalize-exception
Version:
Normalize exceptions/errors
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Markdown
[](https://www.npmjs.com/package/normalize-exception)
[](https://unpkg.com/normalize-exception?module)
[](/src/main.d.ts)
[](https://codecov.io/gh/ehmicky/normalize-exception)
[](https://bundlephobia.com/package/normalize-exception)
[](https://fosstodon.org/@ehmicky)
[](https://medium.com/@ehmicky)
Normalize:
- Exceptions that are [not `Error` instances](#invalid-type)
- Error properties (`name`, `message`, `stack`, `constructor`) that are
[missing](#missing-properties), [invalid](#invalid-properties),
[enumerable](#enumerable-properties), [readonly](#readonly-properties),
[non-writable](#non-writable-properties),
[non-configurable](#non-configurable-properties),
[non-extensible](#non-extensible-error), [proxied](#proxies) or
[throwing](#throwing-properties)
- [`error.cause`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause)
and
[`error.errors`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AggregateError)
[recursively](#recursion), when present
# Example
<!-- eslint-disable no-throw-literal -->
```js
import normalizeException from 'normalize-exception'
try {
throw 'message'
} catch (error) {
console.log(error) // 'message'
console.log(normalizeException(error)) // Error: message
console.log(normalizeException(error) instanceof Error) // true
}
```
# Install
```bash
npm install normalize-exception
```
This package works in both Node.js >=18.18.0 and
[browsers](https://raw.githubusercontent.com/ehmicky/dev-tasks/main/src/browserslist).
This is an ES module. It must be loaded using
[an `import` or `import()` statement](https://gist.github.com/sindresorhus/a39789f98801d908bbc7ff3ecc99d99c),
not `require()`. If TypeScript is used, it must be configured to
[output ES modules](https://www.typescriptlang.org/docs/handbook/esm-node.html),
not CommonJS.
# API
## normalizeException(error, options?)
`error` `any`\
`options` [`Options`](#options)\
_Return value_: `Error`
`normalizeException()` never throws.
If `error` is an `Error` instance, it is returned. Any missing or invalid error
property is directly modified.
If it is not an `Error` instance, a new one is created and returned.
### Options
Options are an optional object with the following properties.
#### shallow
_Type_: `boolean`\
_Default_: `false`
Unless `true`,
[`error.cause`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error/cause)
and
[`error.errors`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/AggregateError)
are normalized [recursively](#recursion), when present.
# Features
## Invalid type
### Strings
<!-- eslint-disable no-throw-literal -->
```js
try {
throw 'message'
} catch (error) {
console.log(error) // 'message'
console.log(normalizeException(error)) // Error: message
console.log(normalizeException(error) instanceof Error) // true
}
```
### Plain objects
<!-- eslint-disable no-throw-literal -->
```js
try {
throw { name: 'TypeError', message: 'message' }
} catch (error) {
console.log(normalizeException(error)) // TypeError: message
}
```
### Others
<!-- eslint-disable unicorn/no-null, no-throw-literal -->
```js
try {
throw null
} catch (error) {
console.log(error.message) // Throws
console.log(normalizeException(error).message) // 'null'
}
```
## Missing properties
```js
try {
const error = new TypeError('message')
error.name = undefined
throw error
} catch (error) {
console.log(error.name) // undefined
console.log(normalizeException(error).name) // 'TypeError'
}
```
## Mismatched constructor
<!-- eslint-disable fp/no-delete -->
```js
try {
const error = new TypeError('message')
error.constructor = RangeError
throw error
} catch (error) {
console.log(error.constructor) // RangeError
console.log(normalizeException(error).constructor) // TypeError
}
```
## Missing stack
```js
try {
const error = new Error('message')
error.stack = undefined
throw error
} catch (error) {
console.log(error.stack) // undefined
console.log(normalizeException(error).stack) // 'Error: message ...'
}
```
## Invalid properties
```js
try {
const error = new Error('message')
error.message = true
throw error
} catch (error) {
console.log(typeof error.message) // 'boolean'
console.log(typeof normalizeException(error).message) // 'string'
}
```
## Enumerable properties
<!-- eslint-disable fp/no-class, fp/no-this, fp/no-mutation -->
```js
class ExampleError extends Error {
constructor(...args) {
super(...args)
// Common mistake: this makes `error.name` enumerable
this.name = 'ExampleError'
}
}
try {
throw new ExampleError('message')
} catch (error) {
console.log({ ...error }) // { name: 'ExampleError' }
console.log({ ...normalizeException(error) }) // {}
}
```
## Readonly properties
<!-- eslint-disable fp/no-mutating-methods, fp/no-get-set, fp/no-mutation -->
```js
try {
const error = new Error('message')
Object.defineProperty(error, 'message', { get: () => 'message' })
throw error
} catch (error) {
error.message = 'other' // Throws
normalizeException(error).message = 'other' // Does not throw
}
```
## Non-writable properties
<!-- eslint-disable fp/no-mutating-methods, fp/no-mutation -->
```js
try {
const error = new Error('message')
Object.defineProperty(error, 'message', { value: '', writable: false })
throw error
} catch (error) {
error.message = 'other' // Throws
normalizeException(error).message = 'other' // Does not throw
}
```
## Non-configurable properties
<!-- eslint-disable fp/no-mutating-methods, fp/no-delete -->
```js
try {
const error = new Error('message')
Object.defineProperty(error, 'message', { value: '', configurable: false })
throw error
} catch (error) {
delete error.message // Throws
delete normalizeException(error).message // Does not throw
}
```
## Non-extensible error
<!-- eslint-disable fp/no-mutation -->
```js
try {
const error = new Error('message')
Object.preventExtensions(error)
throw error
} catch (error) {
error.prop = true // Throws
normalizeException(error).prop = true // Does not throw
}
```
## Proxies
<!-- eslint-disable fp/no-proxy, no-shadow -->
```js
try {
throw new Proxy(new Error('message'), {})
} catch (error) {
const { toString } = Object.prototype
console.log(toString.call(error)) // '[object Object]'
console.log(toString.call(normalizeException(error))) // '[object Error]'
}
```
## Throwing properties
### Proxies
<!-- eslint-disable fp/no-proxy, no-shadow -->
```js
try {
throw new Proxy(new Error('message'), {
get: () => {
throw new Error('example')
},
})
} catch (error) {
console.log(error.message) // Throws
console.log(normalizeException(error).message) // Does not throw
}
```
### Getters
<!-- eslint-disable fp/no-mutating-methods, fp/no-get-set -->
```js
try {
const error = new Error('message')
Object.defineProperty(error, 'message', {
get: () => {
throw new Error('example')
},
})
throw error
} catch (error) {
console.log(error.message) // Throws
console.log(normalizeException(error).message) // Does not throw
}
```
## Recursion
### `error.cause`
```js
try {
throw new Error('message', { cause: 'innerError' })
} catch (error) {
console.log(error.cause instanceof Error) // false
console.log(normalizeException(error).cause instanceof Error) // true
}
```
### `error.errors`
```js
try {
throw new AggregateError(['innerError'], 'message')
} catch (error) {
console.log(error.errors[0] instanceof Error) // false
console.log(normalizeException(error).errors[0] instanceof Error) // true
}
```
# Related projects
- [`modern-errors`](https://github.com/ehmicky/modern-errors): Handle errors in
a simple, stable, consistent way
- [`error-custom-class`](https://github.com/ehmicky/error-custom-class): Create
one error class
- [`error-class-utils`](https://github.com/ehmicky/error-class-utils): Utilities
to properly create error classes
- [`error-serializer`](https://github.com/ehmicky/error-serializer): Convert
errors to/from plain objects
- [`merge-error-cause`](https://github.com/ehmicky/merge-error-cause): Merge an
error with its `cause`
- [`is-error-instance`](https://github.com/ehmicky/is-error-instance): Check if
a value is an `Error` instance
- [`set-error-class`](https://github.com/ehmicky/set-error-class): Properly
update an error's class
- [`set-error-message`](https://github.com/ehmicky/set-error-message): Properly
update an error's message
- [`wrap-error-message`](https://github.com/ehmicky/wrap-error-message):
Properly wrap an error's message
- [`set-error-props`](https://github.com/ehmicky/set-error-props): Properly
update an error's properties
- [`set-error-stack`](https://github.com/ehmicky/set-error-stack): Properly
update an error's stack
- [`error-cause-polyfill`](https://github.com/ehmicky/error-cause-polyfill):
Polyfill `error.cause`
- [`handle-cli-error`](https://github.com/ehmicky/handle-cli-error): 💣 Error
handler for CLI applications 💥
- [`log-process-errors`](https://github.com/ehmicky/log-process-errors): Show
some ❤ to Node.js process errors
- [`error-http-response`](https://github.com/ehmicky/error-http-response):
Create HTTP error responses
- [`winston-error-format`](https://github.com/ehmicky/winston-error-format): Log
errors with Winston
# Support
For any question, _don't hesitate_ to [submit an issue on GitHub](../../issues).
Everyone is welcome regardless of personal background. We enforce a
[Code of conduct](CODE_OF_CONDUCT.md) in order to promote a positive and
inclusive environment.
# Contributing
This project was made with ❤️. The simplest way to give back is by starring and
sharing it online.
If the documentation is unclear or has a typo, please click on the page's `Edit`
button (pencil icon) and suggest a correction.
If you would like to help us fix a bug or add a new feature, please check our
[guidelines](CONTRIBUTING.md). Pull requests are welcome!
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