docs/api/errors.md
---
outline: deep
---
# Errors
<Badges>
[](https://www.npmjs.com/package/@feathersjs/errors)
[](https://github.com/feathersjs/feathers/blob/dove/packages/errors/CHANGELOG.md)
</Badges>
```
npm install @feathersjs/errors --save
```
The `@feathersjs/errors` module contains a set of standard error classes used by all other Feathers modules.
## Examples
Here are a few ways that you can use them:
```ts
import { NotFound, GeneralError, BadRequest } from '@feathersjs/errors'
// If you were to create an error yourself.
const notFound = new NotFound('User does not exist')
// You can wrap existing errors
const existing = new GeneralError(new Error('I exist'))
// You can also pass additional data
const data = new BadRequest('Invalid email', {
email: 'sergey@google.com'
})
// You can also pass additional data without a message
const dataWithoutMessage = new BadRequest({
email: 'sergey@google.com'
})
// If you need to pass multiple errors
const validationErrors = new BadRequest('Invalid Parameters', {
errors: { email: 'Email already taken' }
})
// You can also omit the error message and we'll put in a default one for you
const validationErrors = new BadRequest({
errors: {
email: 'Invalid Email'
}
})
```
## Feathers errors
The following error types, all of which are instances of `FeathersError`, are available:
- 400: `BadRequest`
- 401: `NotAuthenticated`
- 402: `PaymentError`
- 403: `Forbidden`
- 404: `NotFound`
- 405: `MethodNotAllowed`
- 406: `NotAcceptable`
- 408: `Timeout`
- 409: `Conflict`
- 411: `LengthRequired`
- 422: `Unprocessable`
- 429: `TooManyRequests`
- 500: `GeneralError`
- 501: `NotImplemented`
- 502: `BadGateway`
- 503: `Unavailable`
<BlockQuote type="tip">
All of the Feathers core modules and most plugins and database adapters automatically emit the appropriate Feathers errors for you. For example, most of the database adapters will already send `Conflict` or `Unprocessable` errors on validation errors.
</BlockQuote>
Feathers errors contain the following fields:
- `name` - The error name (e.g. "BadRequest", "ValidationError", etc.)
- `message` - The error message string
- `code` - The HTTP status code
- `className` - A CSS class name that can be handy for styling errors based on the error type. (e.g. "bad-request" , etc.)
- `data` - An object containing anything you passed to a Feathers error except for the `errors` object and `message`.
- `errors` - An object containing whatever was passed to a Feathers error inside `errors`. This is typically validation errors or if you want to group multiple errors together.
<BlockQuote type="warning" label="Important">
To convert a Feathers error back to an object call `error.toJSON()`. A normal `console.log` of a JavaScript Error object will not automatically show those additional properties described above (even though they can be accessed directly).
</BlockQuote>
## Custom errors
You can create custom errors by extending from the `FeathersError` class and calling its constructor with `(message, name, code, className, data)`:
- `message` - The error message
- `name` - The error name (e.g. `MyError`)
- `code` - An [HTTP error code](https://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html)
- `className` - The full name of the error class (e.g. `my-error`)
- `data` - Additional data to include in the error
```ts
import { FeathersError } from '@feathersjs/errors'
class UnsupportedMediaType extends FeathersError {
constructor(message: string, data: any) {
super(message, 'UnsupportedMediaType', 415, 'unsupported-media-type', data)
}
}
const error = new UnsupportedMediaType('Not supported')
console.log(error.toJSON())
```
## Error Handling
It is important to make sure that errors get cleaned up before they go back to the client. [Express error handling middleware](https://docs.feathersjs.com/api/express.html#expresserrorhandler) works only for REST calls. If you want to make sure that ws errors are handled as well, you need to use [application error hooks](hooks.md#application-hooks) which are called on any service call error.
Here is an example error handler you can add to app.hooks errors.
```js
const errors = require('@feathersjs/errors')
const errorHandler = (ctx) => {
if (ctx.error) {
const error = ctx.error
if (!error.code) {
const newError = new errors.GeneralError('server error')
ctx.error = newError
return ctx
}
if (error.code === 404 || process.env.NODE_ENV === 'production') {
error.stack = null
}
return ctx
}
}
```
then add it as an [application level](./application.md#hooks-hooks) error hook
```ts
app.hooks({
//...
error: {
all: [errorHandler]
}
})
```