# @ohos.power (Power Management)

The **power** module provides APIs for rebooting and shutting down the system, as well as querying the screen status.

> **NOTE**
>
> The initial APIs of this module are supported since API version 7. Newly added APIs will be marked with a superscript to indicate their earliest API version.

## Modules to Import

```js
import {power} from '@kit.BasicServicesKit';
```

## power.isActive<sup>9+</sup>

isActive(): boolean

Checks whether the current device is active. In the active state, the screen is on if the device has a screen and the device is not in sleep state if the device does not have a screen.

**System capability:** SystemCapability.PowerManager.PowerManager.Core

**Error codes**

For details about the error codes, see [Power Manager Error Codes](errorcode-power.md).

| ID  | Error Message   |
|---------|---------|
| 4900101 | Failed to connect to the service. |

**Example**

```js
try {
    let isActive = power.isActive();
    console.info('power is active: ' + isActive);
} catch(err) {
    console.error('check active status failed, err: ' + err);
}
```

## power.rebootDevice<sup>(deprecated)</sup>

rebootDevice(reason: string): void

> **NOTE**<br>This API is supported since API version 7 and is deprecated since API version 9. The substitute API is available only for system applications.

Reboots a device.

**Required permissions**: ohos.permission.REBOOT (available only for system applications)

**System capability:** SystemCapability.PowerManager.PowerManager.Core


**Parameters**

| Name   | Type    | Mandatory  | Description   |
| ------ | ------ | ---- | ----- |
| reason | string | Yes   | Reason for system reboot.|

**Example**

```js
power.rebootDevice('reboot_test');
```

## power.getPowerMode<sup>9+</sup>

getPowerMode(): DevicePowerMode

Obtains the power mode of this device.

**System capability:** SystemCapability.PowerManager.PowerManager.Core

**Return value**

| Type                                | Description      |
| ------------------------------------ | ---------- |
| [DevicePowerMode](#devicepowermode9) | Power mode.|

**Error codes**

For details about the error codes, see [Power Manager Error Codes](errorcode-power.md).

| ID  | Error Message   |
|---------|---------|
| 4900101 | Failed to connect to the service. |

**Example**

```js
try {
    let mode = power.getPowerMode();
    console.info('power mode: ' + mode);
} catch(err) {
    console.error('get power mode failed, err: ' + err);
}
```

## power.isStandby<sup>10+</sup>

isStandby(): boolean

Checks whether the device is in standby mode.

**System capability:** SystemCapability.PowerManager.PowerManager.Core

**Return value**

| Type               | Description                                  |
| ------------------- | -------------------------------------- |
| boolean | The value **true** indicates that the device is in standby mode, and the value **false** indicates the opposite.|

**Error codes**

For details about the error codes, see [Power Manager Error Codes](errorcode-power.md).

| ID  | Error Message   |
|---------|---------|
| 4900101 | Failed to connect to the service. |

**Example**

```js
try {
    let isStandby = power.isStandby();
    console.info('device is in standby: ' + isStandby);
} catch(err) {
    console.error('check isStandby failed, err: ' + err);
}
```

## power.isScreenOn<sup>(deprecated)</sup>

isScreenOn(callback: AsyncCallback&lt;boolean&gt;): void

> **NOTE**<br>This API is deprecated since API version 9. You are advised to use [power.isActive](#powerisactive9) instead.

Checks the screen status of the current device. This API uses an asynchronous callback to return the result.

**System capability:** SystemCapability.PowerManager.PowerManager.Core

**Parameters**

| Name  | Type                        | Mandatory| Description                                                        |
| -------- | ---------------------------- | ---- | ------------------------------------------------------------ |
| callback | AsyncCallback&lt;boolean&gt; | Yes  | Callback used to return the result. If the operation is successful, **err** is **undefined** and **data** is the screen status obtained, where the value **true** indicates on and the value **false** indicates off. Otherwise, **err** is an error object.|

**Example**

```js
power.isScreenOn((err: Error, data: boolean) => {
    if (typeof err === 'undefined') {
        console.info('screen on status is ' + data);
    } else {
        console.error('check screen status failed, err: ' + err);
    }
})
```

## power.isScreenOn<sup>(deprecated)</sup>

isScreenOn(): Promise&lt;boolean&gt;

> **NOTE**<br>This API is deprecated since API version 9. You are advised to use [power.isActive](#powerisactive9) instead.

Checks the screen status of the current device. This API uses a promise to return the result.

**System capability:** SystemCapability.PowerManager.PowerManager.Core

**Return value**
| Type                  | Description                                              |
| ---------------------- | -------------------------------------------------- |
| Promise&lt;boolean&gt; | Promise used to return the result. The value **true** indicates that the screen is on, and the value **false** indicates the opposite.|

**Example**

```js
power.isScreenOn()
.then((data: boolean) => {
    console.info('screen on status is ' + data);
})
.catch((err: Error) => {
    console.error('check screen status failed, err: ' + err);
})
```

## DevicePowerMode<sup>9+</sup>

Enumerates power modes.

**System capability:** SystemCapability.PowerManager.PowerManager.Core

| Name                   | Value  | Description                  |
| ----------------------- | ---- | ---------------------- |
| MODE_NORMAL             | 600  | Standard mode. It is the default value.|
| MODE_POWER_SAVE         | 601  | Power saving mode.        |
| MODE_PERFORMANCE        | 602  | Performance mode.        |
| MODE_EXTREME_POWER_SAVE | 603  | Ultra power saving mode.    |