# @ohos.app.ability.errorManager (ErrorManager)

The ErrorManager module provides APIs for registering and unregistering error observers.

> **NOTE**
> 
> The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.

## Modules to Import
```ts
import { errorManager } from '@kit.AbilityKit';
```

## errorManager.on('error')

> **NOTE**
> 
> The **errormanager.on** API is registered only in the main thread. Currently, exceptions in child threads (such as TaskPool threads) cannot be captured.
>
> The application does not exit during the use of **errormanager.on**. You are advised to add the synchronous exit operation after the callback function is executed.

on(type: 'error', observer: ErrorObserver): number

Registers an error observer. After the registration, JS crashes generated by the application can be captured. When the application breaks down, the process does not exit.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**
 
| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. It is fixed at **'error'**.|
| observer | [ErrorObserver](js-apis-inner-application-errorObserver.md) | Yes| Digital code of the observer.|

**Return value**

  | Type| Description|
  | -------- | -------- |
  | number | Index of the observer.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |
| 16000003 | The specified ID does not exist. |

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let observer: errorManager.ErrorObserver = {
  onUnhandledException(errorMsg) {
    console.log('onUnhandledException, errorMsg: ', errorMsg);
  },
  onException(errorObj) {
    console.log('onException, name: ', errorObj.name);
    console.log('onException, message: ', errorObj.message);
    if (typeof(errorObj.stack) === 'string') {
      console.log('onException, stack: ', errorObj.stack);
    }
  }
};
let observerId = -1;

try {
  observerId = errorManager.on('error', observer);
} catch (paramError) {
  let code = (paramError as BusinessError).code;
  let message = (paramError as BusinessError).message;
  console.error(`error: ${code}, ${message}`);
}
```

## errorManager.off('error')

off(type: 'error', observerId: number,  callback: AsyncCallback\<void>): void

Unregisters an error observer. This API uses an asynchronous callback to return the result.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**
 
| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. It is fixed at **'error'**.|
| observerId | number | Yes| Index of the observer returned by **on()**.|
| callback | AsyncCallback\<void> | Yes| Callback used to return the result.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |
| 16000003 | The specified ID does not exist. |

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let observerId = 100;

function unregisterErrorObserverCallback(err: BusinessError) {
  if (err) {
    console.error('------------ unregisterErrorObserverCallback ------------', err);
  }
}

try {
  errorManager.off('error', observerId, unregisterErrorObserverCallback);
} catch (paramError) {
  let code = (paramError as BusinessError).code;
  let message = (paramError as BusinessError).message;
  console.error(`error: ${code}, ${message}`);
}
```

## errorManager.off('error')

off(type: 'error', observerId: number): Promise\<void>

Unregisters an error observer. This API uses a promise to return the result.

**Atomic service API**: This API can be used in atomic services since API version 11.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**
 
| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. It is fixed at **'error'**.|
| observerId | number | Yes| Index of the observer returned by **on()**.|

**Return value**

| Type| Description|
| -------- | -------- |
| Promise\<void> | Promise that returns no value.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |
| 16000003 | The specified ID does not exist. |

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';
import { BusinessError } from '@kit.BasicServicesKit';

let observerId = 100;

try {
  errorManager.off('error', observerId)
    .then((data) => {
      console.log('----------- unregisterErrorObserver success ----------', data);
    })
    .catch((err: BusinessError) => {
      console.error('----------- unregisterErrorObserver fail ----------', err);
    });
} catch (paramError) {
  let code = (paramError as BusinessError).code;
  let message = (paramError as BusinessError).message;
  console.error(`error: ${code}, ${message}`);
}
```

## errorManager.on('loopObserver')<sup>12+</sup>

on(type: 'loopObserver', timeout: number, observer: LoopObserver): void

Registers an observer for the message processing duration of the main thread. After the registration, the execution time of a message processed by the main thread of the application can be captured.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**
 
| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. It is fixed at **'loopObserver'**, indicating an observer for the message processing duration of the main thread.|
| timeout | number | Yes|  Event execution threshold, in milliseconds. The value must be greater than **0**.|
| observer | [LoopObserver](js-apis-inner-application-loopObserver.md) | Yes| Observer to register.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';

let observer: errorManager.LoopObserver = {
  onLoopTimeOut(timeout: number) {
    console.log('Duration timeout: ' + timeout);
  }
};

errorManager.on("loopObserver", 1, observer);
```

## errorManager.on('unhandledRejection')<sup>12+</sup>

on(type: 'unhandledRejection', observer: UnhandledRejectionObserver): void

Registers an observer for the promise rejection. After the registration, a rejected promise that is not captured in the current thread of the application can be captured.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**
 
| Name                  | Type                                                         | Mandatory| Description                                      |
|-----------------------|-------------------------------------------------------------| -------- |------------------------------------------|
| type                  | string                                                      | Yes| Event type. It is fixed at **'unhandledRejection'**, indicating an observer for the promise rejection.|
| observer              | [UnhandledRejectionObserver](#unhandledrejectionobserver12) | Yes| Observer to register.                         |

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |
| 16200001 | If the caller is invalid. |

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';

let observer: errorManager.UnhandledRejectionObserver = (reason: Error, promise: Promise<void>) => {
  if (promise === promise1) {
    console.log("promise1 is rejected");
  }
  console.log("reason.name: ", reason.name);
  console.log("reason.message: ", reason.message);
  if (reason.stack) {
    console.log("reason.stack: ", reason.stack);
  }
};

errorManager.on("unhandledRejection", observer);

let promise1 = new Promise<void>(() => {}).then(() => {
  throw new Error("uncaught error");
});
```

## errorManager.off('loopObserver')<sup>12+</sup>

off(type: 'loopObserver', observer?: LoopObserver): void

Unregisters an observer for the message processing duration of the main thread.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**
 
| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| type | string | Yes| Event type. It is fixed at **'loopObserver'**, indicating an observer for the message processing duration of the main thread.|
| observer | [LoopObserver](js-apis-inner-application-loopObserver.md) | No| Observer to unregister.|

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';

errorManager.off("loopObserver");
```

## errorManager.off('unhandledRejection')<sup>12+</sup>

off(type: 'unhandledRejection', observer?: UnhandledRejectionObserver): void

Unregisters an observer for the promise rejection.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**

| Name                  | Type                             | Mandatory| Description                                          |
|-----------------------|---------------------------------|----|----------------------------------------------|
| type                  | string                          | Yes | Event type. It is fixed at **'unhandledRejection'**, indicating an observer for the promise rejection.|
| observer              | [UnhandledRejectionObserver](#unhandledrejectionobserver12) | No | Observer to unregister.                       |

**Error codes**

For details about the error codes, see [Universal Error Codes](../errorcode-universal.md) and [Ability Error Codes](errorcode-ability.md).

| ID| Error Message|
| ------- | -------- |
| 401      | Parameter error. Possible causes: 1. Mandatory parameters are left unspecified; 2.Incorrect parameter types; 3. Parameter verification failed.   |
| 16200001 | If the caller is invalid. |
| 16300004 | If the observer does not exist. |

For details about the error codes, see [Ability Error Codes](errorcode-ability.md).

**Example**
    
```ts
import { errorManager } from '@kit.AbilityKit';

let observer: errorManager.UnhandledRejectionObserver = (reason: Error, promise: Promise<void>) => {
  if (promise === promise1) {
    console.log("promise1 is rejected");
  }
  console.log("reason.name: ", reason.name);
  console.log("reason.message: ", reason.message);
  if (reason.stack) {
    console.log("reason.stack: ", reason.stack);
  }
};

errorManager.on("unhandledRejection", observer);

let promise1 = new Promise<void>(() => {}).then(() => {
  throw new Error("uncaught error")
})

errorManager.off("unhandledRejection");
```
Or:
```ts
import { errorManager } from '@kit.AbilityKit';

let observer: errorManager.UnhandledRejectionObserver = (reason: Error, promise: Promise<void>) => {
  if (promise === promise1) {
    console.log("promise1 is rejected");
  }
  console.log("reason.name: ", reason.name);
  console.log("reason.message: ", reason.message);
  if (reason.stack) {
    console.log("reason.stack: ", reason.stack);
  }
};

errorManager.on("unhandledRejection", observer);

let promise1 = new Promise<void>(() => {}).then(() => {
  throw new Error("uncaught error")
})

errorManager.off("unhandledRejection", observer);
```

## UnhandledRejectionObserver<sup>12+</sup>

type UnhandledRejectionObserver = (reason: Error | any, promise: Promise\<any>) => void

Defines an observer to capture the cause of a rejected promise.

**Atomic service API**: This API can be used in atomic services since API version 12.

**System capability**: SystemCapability.Ability.AbilityRuntime.Core

**Parameters**

| Name   | Type           | Mandatory| Description|
|--------|---------------|---| -------- |
| reason | Error \| any  | Yes| Generally, the value is of the **Error** type, indicating the reason for rejection.|
| promise | Promise\<any> | Yes| Rejected promise.|