> For the complete documentation index, see [llms.txt](https://kernel-js.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://kernel-js.gitbook.io/docs/exceptions/kernel-exceptions.md).

# @kernel/exceptions

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> Common error classes

* Suite of node.js Error classes like most other modern languages
* Generate your own custom Error classes
* Map HTTP status codes to Errors for automatic handling responses from web services and applications
* Suitable to run on browsers (client-side)

## Install

`npm install @kernel/exceptions`

## Class Directory

#### Common Error Classes

* AlreadyInUseError
* ArgumentError
* ArgumentNullError
* AuthenticationRequiredError
* ConnectionError
* DataError
* ForbiddenError
* HttpError
* InvalidOperationError
* SocketError
* NotFoundError
* NotImplementedError
* NotPermittedError
* NotSupportedError
* RangeError
* ReferenceError
* SyntaxError
* TimeoutError
* TypeError
* URIError

## Error Classes

### AlreadyInUseError

Applicable when a resource is already in use, for example unique key constraints like a username.

```
new AlreadyInUseError(entityName, [arg1, arg2, arg3, ..., error])
```

**Arguments**

* `entityName` - the entity that owns the protected resource
* `args` - the fields or attributes that are already in use
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new AlreadyInUseError('user', 'username');
```

### ArgumentError

Applicable when there's a generic problem with an argument received by a function call.

```
new ArgumentError(argumentName[, error])
```

**Arguments**

* `argumentName` - the name of the argument that has a problem
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new ArgumentError('username', 500, err);
```

### ArgumentNullError

Applicable when an argument received by a function call is null/undefined or empty.

```
new ArgumentNullError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new ArgumentNullError('username', 400, err);
```

### AuthenticationRequiredError

Applicable when an operation requires authentication

```
new AuthenticationRequiredError(message, [code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new AuthenticationRequiredError("Please provide authentication.", 403, err);
```

### ConnectionError

Applicable when an error occurs on a connection.

```
new ConnectionError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new ConnectionError('WebService unavailable');
throw new ConnectionError('Database connection no longer available', 500, err);
```

### DataError

Applicable when an error occurs on or with an external data source.

```
new DataError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new DataError('Too many rows returned from database', 500, err);
```

### ForbiddenError

Applicable when an operation is not permitted

```
new ForbiddenError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new NotPermittedError("username cannot be changed once set.", 403, err);
```

### HttpError

Represents a message and a HTTP status code.

```
new HttpError(code[, message, codeMap, error])
```

**Arguments**

* `code` - any HTTP status code integer
* `message` - any message
* `codeMap` - the mapping of error codes and their classes
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Default example
throw new HttpError(404);

// Example with error
throw new HttpError(404, err);

// Example with message and error
throw new HttpError(404, "Not Found", err);

// Example with custom codeMap and error
throw new HttpError(404, {
  400: 'ArgumentError',
  401: 'AuthenticationRequiredError',
  403: 'ForbiddenError',
  404: 'NotFoundError',
  405: 'NotSupportedError',
  409: 'AlreadyInUseError',
}, err);
```

### InvalidOperationError

Applicable when an invalid operation occurs.

```
new InvalidOperationError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new InvalidOperationError('Divide by zero', 500, err);
```

### NotFoundError

Applicable when an attempt to retrieve data yielded no result.

```
new NotFoundError(entity_name[, code, error])
```

**Arguments**

* `entity_name` - a description for what was not found
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new NotFoundError("User", 500, err);
```

### NotImplementedError

Applicable when a requested method or operation is not implemented.

```
new NotImplementedError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new NotImplementedError("Method is not yet implemented.", 500, err);
```

### NotSupportedError

Applicable when a certain condition is not supported by your application.

```
new NotSupportedError(message[, code, error])
```

**Arguments**

* `message` - a message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new NotSupportedError('Zero values', 500, err);
```

### RangeError

Represents an error that occurs when a numeric variable or parameter is outside of its valid range. This is roughly the same as the native RangeError class. It additionally supports an code attribute.

```
new RangeError(message[, code, error])
```

**Arguments**

* `message` - a message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new RangeError("Value must be between " + MIN + " and " + MAX, err);
```

### ReferenceError

Represents an error when a non-existent variable is referenced. This is roughly the same as the native ReferenceError class. It additionally supports an code attribute.

```
new ReferenceError(message[, code, error])
```

**Arguments**

* `message` - a message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new ReferenceError("x is not defined", 500, err);
```

### SocketError

Applicable when an error occurs on a socket.

```
new SocketError(message[, code, error])
```

**Arguments**

* `message` - any message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new SocketError('Socket no longer available', 500, err);
```

### SyntaxError

Represents an error when trying to interpret syntactically invalid code. This is roughly the same as the native SyntaxError class. It additionally supports an code attribute.

```
new SyntaxError(message[, code, error])
```

**Arguments**

* `message` - a message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new SyntaxError("Unexpected token a", 500, err);
```

### TimeoutError

Applicable when an operation takes longer than the alloted amount.

```
new TimeoutError(time[, code, error])
```

**Arguments**

* `time` - a time duration
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new TimeoutError('100ms', 500, err);
```

### TypeError

Represents an error when a value is not of the expected type. This is roughly the same as the native TypeError class. It additionally supports an code attribute.

```
new TypeError(message[, code, error])
```

**Arguments**

* `message` - a message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new TypeError("number is not a function", 500, err);
```

### URIError

Represents an error when a value is not of the expected type. This is roughly the same as the native URIError class. It additionally supports an code attribute.

```
new URIError(message[, code, error])
```

**Arguments**

* `message` - a message
* `code` - the error code
* `error` - the Error instance that caused the current error. Stack trace will be appended

```javascript
// Example
throw new URIError("URI malformed", 500, err);
```