js-apis-distributed-data.md

# Distributed Data Management

>![](../../public_sys-resources/icon-note.gif) **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

```
import distributedData from '@ohos.data.distributedData';
```
## System Capabilities
SystemCapability.DistributedDataManager.KVStore.DistributedKVStore




## distributedData.createKVManager

createKVManager(config: KVManagerConfig, callback: AsyncCallback<KVManager>): void

Creates a **KVManager** object to manage key-value (KV) stores. This method uses an asynchronous callback to return the result.

- Parameters

| Name| Type| Mandatory| Description|
| ----- | ------ | ------ | ------ |
| config | [KVManagerConfig](#kvmanagerconfig) | Yes| Configuration of the **KVManager** object, including the bundle name and user information of the caller.|
| callback | AsyncCallback<[KVManager](#kvmanager)> | Yes| Callback invoked to return the **KVManager** object created.|


-   Example

    ```
    let kvManager;
    try {
        const kvManagerConfig = {
            bundleName : 'com.example.datamanagertest',
            userInfo : {
                userId : '0',
                userType : distributedData.UserType.SAME_USER_ID
            }
        }
        distributedData.createKVManager(kvManagerConfig, function (err, manager) {
            if (err) {
                console.log("createKVManager err: "  + JSON.stringify(err));
                return;
            }
            console.log("createKVManager success");
            kvManager = manager;
        });
    } catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```

## distributedData.createKVManager

createKVManager(config: KVManagerConfig): Promise<KVManager>

Creates a **KVManager** object to manage KV stores. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| ----- | ------ | ------ | ------ |
| config |[KVManagerConfig](#kvmanager) | Yes| Configuration of the **KVManager** object, including the bundle name and user information of the caller.|

-   Return value

| Type| Description|
| -------- | -------- |
| Promise<[KVManager](#kvmanager)> | Promise used to return the **KVManager** object created.|

-   Example

    ```
    let kvManager;
    try {
        const kvManagerConfig = {
            bundleName : 'com.example.datamanagertest',
            userInfo : {
                userId : '0',
                userType : distributedData.UserType.SAME_USER_ID
            }
        }
        distributedData.createKVManager(kvManagerConfig).then((manager) => {
            console.log("createKVManager success");
            kvManager = manager;
        }).catch((err) => {
            console.log("createKVManager err: "  + JSON.stringify(err));
        });
    } catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


## KVManagerConfig

Provides configuration of the **KVManager** object, including the bundle name and user information of the caller.

| Name| Type| Mandatory| Description|
| ----- | ------ | ------ | ------ |
| userInfo | [UserInfo](#userinfo) | Yes| User information.|
| bundleName | string | Yes| Bundle name.|



## UserInfo

Defines user information.

| Name| Type| Mandatory| Description|
| ----- | ------ | ------ | ------ |
| userId | string | Yes| User ID.|
| userType | [UserType](#usertype) | Yes| User type.|


## UserType

Defines the user type.

| Name| Default Value| Description|
| ----- | ------ | ------ |
| SAME\_USER_ID| 0 | User who logs in to different devices using the same account.|


## KVManager

Creates a **KVManager** object to obtain KV store information. Before calling any method in **KVManager**, you must use **createKVManager** to create a **KVManager** object.

### getKVStore

getKVStore<T extends KVStore>(storeId: string, options: Options, callback: AsyncCallback&lt;T&gt;): void

Creates and obtains a KV store. This method uses an asynchronous callback to return the result.

- Parameters

| Name| Type| Mandatory| Description|
| ----- | ------ | ------ | ------ |
| storeId | string | Yes| Unique identifier of the KV store. The length cannot exceed [MAX\_STORE\_ID\_LENGTH](#constants).|
| options | [Options](#options) | Yes| Configuration of the KV store.|
| callback | AsyncCallback&lt;T&gt;, &lt;T extends KVStore&gt;| Yes| Callback invoked to return the KV store created.|

-   Example

    ```
    let kvStore;
    let kvManager;
    try {
        const options = {
            createIfMissing : true,
            encrypt : false,
            backup : false,
            autoSync : true,
            kvStoreType : distributedData.KVStoreType.SINGLE_VERSION,
            securityLevel : distributedData.SecurityLevel.S2,
        };
        kvManager.getKVStore('storeId', options, function (err, store) {
            if (err) {
                console.log("getKVStore err: "  + JSON.stringify(err));
                return;
            }
            console.log("getKVStore success");
            kvStore = store;
        });
    } catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### getKVStore

getKVStore&lt;T extends KVStore&gt;(storeId: string, options: Options): Promise&lt;T&gt;

Creates and obtains a KV store. This method uses a promise to return the result.

- Parameters

| Name| Type| Mandatory| Description|
| ------- | ---------------------- | ---- | -------------------- |
| storeId  | string      | Yes| Unique identifier of the KV store. The length cannot exceed [MAX\_STORE\_ID\_LENGTH](#constants).|
| options  | [Options](#options)   | Yes| Configuration of the KV store.|


-   Return value

| Type| Description|
| -------------------------------------- | ------------------------ |
| Promise&lt;T&gt; &lt;T extends KVStore&gt; | Promise used to return the KV store created.|


- Example

  ```
  let kvStore;
  let kvManager;
  try {
      const options = {
          createIfMissing : true,
          encrypt : false,
          backup : false,
          autoSync : true,
          kvStoreType : distributedData.KVStoreType.SINGLE_VERSION,
          securityLevel : distributedData.SecurityLevel.S2,
      };
      kvManager.getKVStore('storeId', options).then((store) => {
          console.log("getKVStore success");
          kvStore = store;
      }).catch((err) => {
          console.log("getKVStore err: "  + JSON.stringify(err));
      });
  } catch (e) {
      console.log("An unexpected error occurred. Error:" + e);
  }
  ```

### closeKVStore<sup>8+</sup> ###

closeKVStore(appId: string, storeId: string, kvStore: KVStore, callback: AsyncCallback&lt;void&gt;): void;

Closes a KV store. This method uses an asynchronous callback to return the result.

- Parameters


| Name| Type| Mandatory| Description|
| ------- | -----------------   | ---- | --------------------------- |
| appId    | string              | Yes| Bundle name of the app that invokes the KV store.|
| storeId  | string  | Yes| Unique identifier of the KV store to close. The length cannot exceed the value of [MAX\_STORE\_ID_LENGTH](#constants).|
| kvStore  | [KVStore](#kvstore) | Yes| KV store to close.|
| callback | AsyncCallback&lt;void&gt; | Yes| Callback used to return the result. If the KV store is closed, **true** will be returned. Otherwise, **false** will be returned.|


-   Example

    ```
    let kvStore;
    let kvManager;
    const options = {
        createIfMissing : true,
        encrypt : false,
        backup : false,
        autoSync : true,
        kvStoreType : distributedData.KVStoreType.SINGLE_VERSION,
        schema : '',
        securityLevel : distributedData.SecurityLevel.S2,
    }
    try {
        kvManager.getKVStore('storeId', options, async function (err, store) {
            console.log('getKVStore success');
            kvStore = store;
            await kvManager.closeKVStore('appId', 'storeId', kvStore, function (err, data) {
                console.log('closeKVStore success');
            });
        });
    } catch (e) {
        console.log('closeKVStore e ' + e);
    }
    ```

### closeKVStore<sup>8+</sup> ###

closeKVStore(appId: string, storeId: string, kvStore: KVStore): Promise&lt;void&gt;;

Closes a KV store. This method uses a promise to return the result.

- Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ---- | ----------------------------- |
| appId  | string  | Yes| Bundle name of the app that invokes the KV store.|
| storeId | string | Yes| Unique identifier of the KV store to close. The length cannot exceed the value of [MAX\_STORE\_ID_LENGTH](#constants).|
| kvStore | [KVStore](#kvstore)  | Yes| KV store to close.|

- Return value

| Type| Description|
| ------------- | -------------- |
| Promise<void> | Promise used to return the result. If the KV store is closed, **true** will be returned. Otherwise, **false** will be returned.|

-   Example

    ```
    let kvManager;
    let kvStore;
    const options = {
        createIfMissing : true,
        encrypt : false,
        backup : false,
        autoSync : true,
        kvStoreType : distributedData.KVStoreType.SINGLE_VERSION,
        schema : '',
        securityLevel : distributedData.SecurityLevel.S2,
    }
    try {
        kvManager.getKVStore('storeId', options).then(async (store) => {
            console.log('getKVStore success');
            kvStore = store;
            await kvManager.closeKVStore('appId', 'storeId', kvStore).then(() => {
                console.log('closeKVStore success');
            }).catch((err) => {
                console.log('closeKVStore err ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('CloseKVStore getKVStore err ' + JSON.stringify(err));
        });
    } catch (e) {
        console.log('closeKVStore e ' + e);
    }
    ```


### deleteKVStore<sup>8+</sup> ###

deleteKVStore(appId: string, storeId: string, callback: AsyncCallback&lt;void&gt;): void;

Deletes a KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| appId  | string  | Yes| Bundle name of the app that invokes the KV store.|
| storeId | string | Yes| Unique identifier of the KV store to delete. The length cannot exceed the value of [MAX\_STORE\_ID_LENGTH](#constants).|
| callback | AsyncCallback&lt;void&gt;  | Yes| Callback used to return the result. If the KV store is deleted, **true** will be returned. Otherwise, **false** will be returned.|


-   Example

    ```
    let kvManager;
    let kvStore;
    const options = {
        createIfMissing : true,
        encrypt : false,
        backup : false,
        autoSync : true,
        kvStoreType : distributedData.KVStoreType.SINGLE_VERSION,
        schema : '',
        securityLevel : distributedData.SecurityLevel.S2,
    }
    try {
        kvManager.getKVStore('store', options, async function (err, store) {
            console.log('getKVStore success');
            kvStore = store;
            await kvManager.deleteKVStore('appId', 'storeId', function (err, data) {
                console.log('deleteKVStore success');
            });
        });
    } catch (e) {
        console.log('DeleteKVStore e ' + e);
    }
    ```

### deleteKVStore<sup>8+</sup> ###

deleteKVStore(appId: string, storeId: string): Promise&lt;void&gt;;

Deletes a KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| appId  | string  | Yes| Bundle name of the app that invokes the KV store.|
| storeId | string | Yes| Unique identifier of the KV store to delete. The length cannot exceed the value of [MAX\_STORE\_ID_LENGTH](#constants).|


-   Return value

| Type| Description|
| ------------- | -------------- |
| Promise&lt;void&gt; | Promise used to return the result. If the KV store is deleted, **true** will be returned. Otherwise, **false** will be returned.|

-   Example

    ```
    let kvManager;
    let kvStore;
    const options = {
        createIfMissing : true,
        encrypt : false,
        backup : false,
        autoSync : true,
        kvStoreType : distributedData.KVStoreType.SINGLE_VERSION,
        schema : '',
        securityLevel : distributedData.SecurityLevel.S2,
    }
    try {
        kvManager.getKVStore('storId', options).then(async (store) => {
            console.log('getKVStore success');
            kvStore = store;
            await kvManager.deleteKVStore('appId', 'storeId').then(() => {
                console.log('deleteKVStore success');
            }).catch((err) => {
                console.log('deleteKVStore err ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('getKVStore err ' + JSON.stringify(err));
        });
    } catch (e) {
        console.log('deleteKVStore e ' + e);
    }
    ```


### getAllKVStoreId<sup>8+</sup> ###

getAllKVStoreId(appId: string, callback: AsyncCallback&lt;string[]&gt;): void;

Obtains the IDs of all the KV stores that are created using **getKvStore** and have not been deleted using **deleteKvStore**. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| appId  | string  | Yes| Bundle name of the app that invokes the KV store.|
| callback | AsyncCallback&lt;void&gt; | Yes|Callback used to return the KV store IDs obtained. |

-   Example

    ```
    let kvManager;
    try {
        kvManager.getAllKVStoreId('appId', function (err, data) {
            console.log('GetAllKVStoreId success');
            console.log('GetAllKVStoreId size = ' + data.length);
        });
    } catch (e) {
        console.log('GetAllKVStoreId e ' + e);
    }
    ```


### getAllKVStoreId<sup>8+</sup> ###

getAllKVStoreId(appId: string): Promise&lt;string[]&gt;;

Obtains the IDs of all the KV stores that are created using **getKvStore** and have not been deleted using **deleteKvStore**. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| appId  | string  | Yes| Bundle name of the app that invokes the KV store.|


-   Return value

| Type| Description|
| ------------- | -------------- |
| Promise&lt;string[]&gt;| Promise used to return the KV store IDs obtained.|

-   Example

    ```
    let kvManager;
    try {
        console.log('GetAllKVStoreId');
        kvManager.getAllKVStoreId('apppId').then((data) => {
            console.log('getAllKVStoreId success');
            console.log('size = ' + data.length);
        }).catch((err) => {
            console.log('getAllKVStoreId err ' + JSON.stringify(err));
        });
    } catch(e) {
        console.log('getAllKVStoreId e ' + e);
    }
    ```


### on<sup>8+</sup> ###

on(event: 'distributedDataServiceDie', deathCallback: Callback&lt;void&gt;): void;

Subscribes to the **distributedDataServiceDie** events. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| event  | 'distributedDataServiceDie'  | Yes| Type of events to subscribe to. |
| deathCallback  | Callback&lt;void&gt;  | Yes| Callback invoked when the distributed data service is dead.|



-   Example

    ```
    let kvManager;
    try {
        
        console.log('KVManagerOn');
        const deathCallback = function () {
            console.log('death callback call');
        }
        kvManager.on('distributedDataServiceDie', deathCallback);
    } catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### off<sup>8+</sup> ###

off(event: 'distributedDataServiceDie', deathCallback?: Callback&lt;void&gt;): void;

Unsubscribes from the **distributedDataServiceDie** events. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| event  | 'distributedDataServiceDie'  | Yes| Type of events to unsubscribe from. |
| deathCallback  | Callback&lt;void&gt;  | No| Callback used to return the **distributedDataServiceDie** events.|


-   Example

    ```
    let kvManager;
    try {
        console.log('KVManagerOff');
        const deathCallback = function () {
            console.log('death callback call');
        }
        kvManager.off('distributedDataServiceDie', deathCallback);
    } catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    
    ```

## Options

Provides KV store configuration.

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| createIfMissing  | boolean | No| Whether to create a KV store if no database file exists. By default, a KV store is created.|
| encrypt  | boolean | No|Whether to encrypt database files. By default, database files are not encrypted.|
| backup  | boolean | No|Whether to back up database files. By default, database files are backed up. |
| autoSync  | boolean | No|Whether to automatically synchronize database files. By default, database files are not automatically synchronized.|
| kvStoreType | [KVStoreType](#kvstoretype) | No|Type of the KV store to create. By default, a device KV store is created. The device KV store stores data for multiple devices that collaborate with each other.|
| securityLevel | [SecurityLevel](#securitylevel) | No|Security level of the KV store. By default, the security level is not set.|


## KVStoreType

Defines the KV store types.

| Name| Default Value| Description|
| ---   | ----  | ----------------------- |
| DEVICE_COLLABORATION  | 0 | Device KV store.|
| SINGLE_VERSION  | 1 | Single KV store.|
| MULTI_VERSION   | 2 | Multi-version KV store. This type is not supported currently.|



## SecurityLevel

Defines the KV store security levels.

| Name| Default Value| Description|
| ---   | ----  | ----------------------- |
| NO_LEVEL  | 0 | No security level is set for the KV store.|
| S0  | 1 | The KV store security level is public.|
| S1  | 2 | The KV store security level is low. If data leakage occurs, minor impact will be caused on the database.|
| S2  | 3 | The KV store security level is medium. If data leakage occurs, moderate impact will be caused on the database.|
| S3  | 5 | The KV store security level is high. If data leakage occurs, major impact will be caused on the database.|
| S4  | 6 | The KV store security level is critical. If data leakage occurs, severe impact will be caused on the database.|


## Constants

Defines the KV store constants.

| Name| Default Value| Description|
| ---   | ----  | ----------------------- |
| MAX\_KEY_LENGTH| 1024 | Maximum length (in bytes) of a key in the KV store.|
| MAX\_VALUE_LENGTH| 4194303 | Maximum length (in bytes) of a value in the KV store.|
| MAX\_KEY\_LENGTH\_DEVICE| 896 | Maximum length of the device coordinate key.|
| MAX\_STORE\_ID\_LENGTH| 128 | Maximum length (in bytes) of a KV store ID.|
| MAX\_QUERY_LENGTH| 512000 | Maximum query length.|
| MAX\_BATCH_SIZE| 128 | Maximum size of a batch operation.|

## Schema<sup>8+</sup> ##

Defines a database schema. When creating or opening a KV store, you can create **Schema** objects and put them into **Options**.

### toJsonString<sup>8+</sup> ###

toJsonString():string;

Obtains the schema in JSON format.

-   Return value

| Type| Description|
| ------------- | -------------- |
| string |Schema in JSON format obtained.|

-   Example

    ```
    import ddm from '@ohos.data.distributedData';
    try {
        let schema = new ddm.Schema();
        const str = schema.toJsonString();
        console.log("schema: " + str);
    } catch (e) {
       console.log("toJsonString " + e);
    }
    ```


## FieldNode<sup>8+</sup> ##

Defines a node of a **Schema** instance. It provides methods for defining values stored in the KV store.

### appendChild<sup>8+</sup> ###

appendChild(child: FieldNode): boolean;

Adds a child node to this **FieldNode**.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| child  | [FieldNode](#FieldNode)  | Yes| Child node to add.|


-   Return value

| Type| Description|
| ------------- | -------------- |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    import ddm from '@ohos.data.distributedData';
    try {
        let node = new ddm.FieldNode("root");
        let child1 = new ddm.FieldNode("child1");
        let child2 = new ddm.FieldNode("child2");
        let child3 = new ddm.FieldNode("child3");
        node.appendChild(child1);
        node.appendChild(child2);
        node.appendChild(child3);
        console.log("appendNode " + node.toJson());
        child1 = null;
        child2 = null;
        child3 = null;
        node = null;
    } catch (e) {
        console.log("AppendChild " + e);
    }
    ```


### toJson<sup>8+</sup> ###

toJson(): string;

Obtains the field name.

-   Return value

| Type| Description|
| ------ | --------------    |
| string |Field name obtained.|

-   Example

    ```
	import ddm from '@ohos.data.distributedData';
    try {
        let node = new ddm.FieldNode("root");
        let child = new ddm.FieldNode("child");
        node.appendChild(child);
        console.log("appendNode " + node.toJson());
    } catch (e) {
       console.log("ToJson " + e);
    }
    ```


## KvStoreResultSet<sup>8+</sup> ##

Provides methods to obtain the KV store result set and query or move the data read position. Before calling any method in **KvStoreResultSet**, you must use **KvStore** to create a **KvStore** instance.

### getCount<sup>8+</sup> ###

getCount(): number;

Obtains the number of rows in the result set.

-   Return value

| Type| Description|
| ------ | --------------    |
| number |Number of rows obtained.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const count = resultSet.getCount();
        console.log("GetCount " + count);
    } catch (e) {
        console.log("GetCount fail " + e);
    }
    ```


### getPosition<sup>8+</sup> ###

getPosition(): number;

Obtains the current data read position (position from which data is read) in the result set.

-   Return value

| Type| Description|
| ------ | --------------    |
| number |Current data read position obtained.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const positon = resultSet.getPosition();
        console.log("getPosition " + positon);
    } catch (e) {
        console.log("GetPosition fail " + e);
    }
    ```


### moveToFirst<sup>8+</sup> ###

moveToFirst(): boolean;

Moves the data read position to the first row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.moveToFirst();
        console.log("moveToFirst " + moved);
    } catch (e) {
        console.log("MoveToFirst fail " + e);
    }
    ```


### moveToLast<sup>8+</sup> ###

moveToLast(): boolean;

Moves the data read position to the last row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.moveToLast();
        console.log("moveToLast " + moved);
    } catch (e) {
        console.log("moveToLast fail " + e);
    }
    ```


### moveToNext<sup>8+</sup> ###

moveToNext(): boolean;

Moves the data read position to the next row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.moveToNext();
        console.log("moveToNext " + moved);
    } catch (e) {
        console.log("moveToNext fail " + e);
    }
    ```


### moveToPrevious<sup>8+</sup> ###

moveToPrevious(): boolean;

Moves the data read position to the previous row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.moveToPrevious();
        console.log("moveToPrevious " + moved);
    } catch (e) {
        console.log("moveToPrevious fail " + e);
    }
    ```


### move<sup>8+</sup> ###

move(offset: number): boolean;

Moves the data read position with the specified offset from the current position.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| offset  | number  | Yes| Offset to move the data read position. A negative value means to move backward, and a positive value means to move forward.|

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.move();
        console.log("move " + moved);
    } catch (e) {
        console.log("move fail " + e);
    }
    ```


### moveToPosition<sup>8+</sup> ###

moveToPosition(position: number): boolean;

Moves the data read position from 0 to an absolute position.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| position  | number  | Yes|Absolute position to move to.|

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the operation is successful; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.moveToPosition();
        console.log("moveToPosition " + moved);
    } catch (e) {
        console.log("moveToPosition fail " + e);
    }
    ```


### isFirst<sup>8+</sup> ###

isFirst(): boolean;

Checks whether the data read position is the first row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the data read position is the first row; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.isFirst();
        console.log("isFirst " + moved);
    } catch (e) {
        console.log("isFirst fail " + e);
    }
    ```


### isLast<sup>8+</sup> ###

isLast(): boolean;

Checks whether the data read position is the last row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the data read position is the last row; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.isLast();
        console.log("isLast " + moved);
    } catch (e) {
        console.log("isLast fail " + e);
    }
    ```


### isBeforeFirst<sup>8+</sup> ###

isBeforeFirst(): boolean;

Checks whether the data read position is before the first row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the read position is before the first row; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.isBeforeFirst();
        console.log("isBeforeFirst " + moved);
    } catch (e) {
        console.log("isBeforeFirst fail " + e);
    }
    ```


### isAfterLast<sup>8+</sup> ###

isAfterLast(): boolean;

Checks whether the data read position is after the last row.

-   Return value

| Type| Description|
| ------  | --------------    |
| boolean |Returns **true** if the data read position is after the last row; returns **false** otherwise.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.isAfterLast();
        console.log("isAfterLast " + moved);
    } catch (e) {
        console.log("isAfterLast fail " + e);
    }
    ```


### getEntry<sup>8+</sup> ###

getEntry(): Entry;

Obtains KV pairs.

-   Return value

| Type| Description|
| ------  | -------   |
| Entry   |KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
	    let resultSet;
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + err);
        });
        const moved = resultSet.moveToNext();
        const entry  = resultSet.getEntry();
        console.log("getEntry " + JSON.stringify(entry));
    } catch (e) {
        console.log("getEntry fail " + e);
    }
    ```


## Query<sup>8+</sup> ##

Provides methods to create a **Query** object, which defines different data query criteria.

### reset<sup>8+</sup> ###

reset(): Query;

Resets the **Query** object that contains common query options.

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object reset.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.equalTo("key", "value");
        console.log("query is " + query.getSqlLike());
        query.reset();
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("simply calls should be ok :" + e);
    }
    ```


### equalTo<sup>8+</sup> ###

equalTo(field: string, value: number|string|boolean): Query;

Creates a **Query** object to match the specified field whose value is equal to the specified value.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| value  | number/string/boolean  | Yes| Value specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.equalTo("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### notEqualTo<sup>8+</sup> ###

notEqualTo(field: string, value: number|string|boolean): Query;

Creates a **Query** object to match the specified field whose value is not equal to the specified value.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| value  | number/string/boolean  | Yes| Value specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notEqualTo("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### greaterThan<sup>8+</sup> ###

greaterThan(field: string, value: number|string|boolean): Query;

Creates a **Query** object to match the specified field whose value is greater than the specified value.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| value  | number/string/boolean  | Yes| Value specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.greaterThan("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### lessThan<sup>8+</sup> ###

lessThan(field: string, value: number|string): Query;

Creates a **Query** object to match the specified field whose value is less than the specified value.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| value  | number/string/boolean  | Yes| Value specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.lessThan("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### greaterThanOrEqualTo<sup>8+</sup> ###

greaterThanOrEqualTo(field: string, value: number|string): Query;

Creates a **Query** object to match the specified field whose value is greater than or equal to the specified value.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| value  | number/string/boolean  | Yes| Value specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.greaterThanOrEqualTo("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### lessThanOrEqualTo<sup>8+</sup> ###

lessThanOrEqualTo(field: string, value: number|string): Query;

Creates a **Query** object to match the specified field whose value is less than or equal to the specified value.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| value  | number/string/boolean  | Yes| Value specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.lessThanOrEqualTo("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### isNull<sup>8+</sup> ###

isNull(field: string): Query;

Creates a **Query** object to match the specified field whose value is **null**.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.isNull("field");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### inNumber<sup>8+</sup> ###

inNumber(field: string, valueList: number[]): Query;

Creates a **Query** object to match the specified field whose value is within the specified list of numbers.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| valueList  | number[]  | Yes| List of numbers.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|


-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.inNumber("field", [0, 1]);
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### inString<sup>8+</sup> ###

inString(field: string, valueList: string[]): Query;

Creates a **Query** object to match the specified field whose value is within the specified list of strings.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| valueList  | string[]  | Yes| List of strings.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.inString("field", ['test1', 'test2']);
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### notInNumber<sup>8+</sup> ###

notInNumber(field: string, valueList: number[]): Query;

Creates a **Query** object to match the specified field whose value is not within the specified list of numbers.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| valueList  | number[]  | Yes| List of numbers.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notInNumber("field", [0, 1]);
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### notInString<sup>8+</sup> ###

notInString(field: string, valueList: string[]): Query;

Creates a **Query** object to match the specified field whose value is not within the specified list of strings.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| valueList  | string[]  | Yes| List of strings.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notInString("field", ['test1', 'test2']);
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### like<sup>8+</sup> ###

like(field: string, value: string): Query;

Creates a **Query** object to match the specified field whose value is similar to the specified string.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| valueList  | string  | Yes| String specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.like("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### unlike<sup>8+</sup> ###

unlike(field: string, value: string): Query;

Creates a **Query** object to match the specified field whose value is not similar to the specified string.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|
| valueList  | string  | Yes| String specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.unlike("field", "value");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### and<sup>8+</sup> ###

and(): Query;

Creates a **Query** object with the AND condition.

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notEqualTo("field", "value1");
        query.and();
        query.notEqualTo("field", "value2");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### or<sup>8+</sup> ###

or(): Query;

Creates a **Query** object with the OR condition.

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notEqualTo("field", "value1");
        query.or();
        query.notEqualTo("field", "value2");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### orderByAsc<sup>8+</sup> ###

orderByAsc(field: string): Query;

Creates a **Query** object to sort the query results in ascending order.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notEqualTo("field", "value");
        query.orderByAsc("field");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### orderByDesc<sup>8+</sup> ###

orderByDesc(field: string): Query;

Creates a **Query** object to sort the query results in descending order.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field to match. It must start with $ and cannot contain ^.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|


-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notEqualTo("field", "value");
        query.orderByDesc("field");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### limit<sup>8+</sup> ###

limit(total: number, offset: number): Query;

Creates a **Query** object to specify the number of results and where to start.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| total  | number  | Yes|Number of results to query.|
| offset | number  | Yes|Start position for query.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.notEqualTo("field", "value");
        query.limit("total", "offset");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### isNotNull<sup>8+</sup> ###

isNotNull(field: string): Query;

Creates a **Query** object with a specified field that is not null.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| fieId  | string  | Yes|Field specified.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.isNotNull("field");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### beginGroup<sup>8+</sup> ###

beginGroup(): Query;

Creates a **Query** object for a query condition group with a left parenthesis.

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.beginGroup();
        query.isNotNull("field");
        query.endGroup();
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### endGroup<sup>8+</sup> ###

endGroup(): Query;

Creates a **Query** object for a query condition group with a right parenthesis.

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.beginGroup();
        query.isNotNull("field");
        query.endGroup();
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### prefixKey<sup>8+</sup> ###

prefixKey(prefix: string): Query;

Creates a **Query** object with a specified key prefix.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| prefix | string  | Yes|Key prefix.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.prefixKey("$.name");
        query.prefixKey("0");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
        console.log("dumplicated calls should be ok :" + e);
    }
    ```


### setSuggestIndex<sup>8+</sup> ###

setSuggestIndex(index: string): Query;

Creates a **Query** object with an index preferentially used for query.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| index  | string  | Yes|Index preferentially used for query.|

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.setSuggestIndex("$.name");
        query.setSuggestIndex("0");
        console.log("query is " + query.getSqlLike());
        query = null;
    } catch (e) {
       console.log("dumplicated calls should be ok :" + e);
    }
    ```


### deviceId<sup>8+</sup> ###

deviceId(deviceId:string):Query;

Creates a **Query** object with the device ID as the key prefix.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| deviceId | string  | Yes|Device ID.|


-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object created.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        query.deviceId("deviceId");
        console.log("query is " + query.getSqlLike());
    } catch (e) {
        console.log("should be ok on Method Chaining : " + e);
    }
    ```


### getSqlLike<sup>8+</sup> ###

getSqlLike():string;

Obtains the query statement of this **Query** object.

-   Return value

| Type| Description|
| ------  | -------   |
| [Query](#querysup8sup) |**Query** object.|

-   Example

    ```
    try {
        let query = new distributedData.Query();
        let sql1 = query.getSqlLike();
        console.log("GetSqlLike sql=" + sql1);
    } catch (e) {
        console.log("dumplicated calls should be ok : " + e);
    }
    ```


## KVStore

Provides methods to manage data in a KV store, for example, adding or deleting data and subscribing to data changes or completion of data synchronization. Before calling any method in **KVStore**, you must use **getKVStore** to obtain a **KVStore** object.

### put

put(key: string, value: Uint8Array | string | number | boolean, callback: AsyncCallback&lt;void&gt;): void

Adds a KV pair of the specified type to this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| key    | string  | Yes|Key of the KV pair to add. It cannot be empty, and the length cannot exceed [MAX\_KEY\_LENGTH](#constants).|
| value  | Uint8Array / string / number / boolean  | Yes|Value of the KV pair to add. The value type can be Uint8Array, number, string, or boolean. A value of the Uint8Array or string type cannot exceed [MAX\_VALUE\_LENGTH](#constants).|


-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-test-string';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, function (err,data) {
            if (err != undefined) {
                console.log("put err: " + JSON.stringify(err));
                return;
            }
            console.log("put success");
        });
    }catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### put

put(key: string, value: Uint8Array | string | number | boolean): Promise&lt;void&gt;

Adds a KV pair of the specified type to this KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| key    | string  | Yes|Key of the KV pair to add. It cannot be empty, and the length cannot exceed [MAX\_KEY\_LENGTH](#constants).|
| value  | Uint8Array / string / number / boolean  | Yes|Value of the KV pair to add. The value type can be Uint8Array, number, string, or boolean. A value of the Uint8Array or string type cannot exceed [MAX\_VALUE\_LENGTH](#constants).|

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|


-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-test-string';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT).then((data) => {
            console.log("put success: " + JSON.stringify(data));
        }).catch((err) => {
            console.log("put err: " + JSON.stringify(err));
        });
    }catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### delete

delete(key: string, callback: AsyncCallback&lt;void&gt;): void

Deletes a KV pair from this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| key    | string  | Yes|Key of the KV pair to delete. It cannot be empty, and the length cannot exceed [MAX\_KEY\_LENGTH](#constants).|
| callback  | AsyncCallback&lt;void&gt;  | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-test-string';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, function (err,data) {
            if (err != undefined) {
                console.log("put err: " + JSON.stringify(err));
                return;
            }
            console.log("put success");
            kvStore.delete(KEY_TEST_STRING_ELEMENT, function (err,data) {
                if (err != undefined) {
                    console.log("delete err: " + JSON.stringify(err));
                    return;
                }
                console.log("delete success");
            });
        });
    }catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### delete

delete(key: string): Promise&lt;void&gt;

Deletes a KV pair from this KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| key    | string  | Yes|Key of the KV pair to delete. It cannot be empty, and the length cannot exceed [MAX\_KEY\_LENGTH](#constants).|

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-test-string';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT).then((data) => {
            console.log("put success: " + JSON.stringify(data));
            kvStore.delete(KEY_TEST_STRING_ELEMENT).then((data) => {
                console.log("delete success");
            }).catch((err) => {
                console.log("delete err: " + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log("put err: " + JSON.stringify(err));
        });
    }catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### on

on(event: 'dataChange', type: SubscribeType, observer: Callback&lt;ChangeNotification&gt;): void

Subscribes to data changes of the specified type. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| event  |'dataChange'  | Yes|Type of the events to subscribe to.|
| type  |[SubscribeType](#subscribetypea) | Yes|Type of data changes.|
| observer |Callback&lt;[ChangeNotification](#changenotificationa)&gt; | Yes|Callback used to return the result.|


-   Example

    ```
    let kvStore;
    kvStore.on('dataChange', distributedData.SubscribeType.SUBSCRIBE_TYPE_LOCAL, function (data) {
        console.log("dataChange callback call data: " + JSON.stringify(data));
    });
    ```


### on

on(event: 'syncComplete', syncCallback: Callback<Array&lt;[string, number]&gt;): void

Subscribes to data synchronization completion events. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| event  |'syncComplete' | Yes|Type of the events to subscribe to.|
| syncCallback  |Callback&lt;Array&lt;[string, number]&gt; | Yes|Callback used to return the result.|


-   Example

    ```
    let kvStore;
    kvStore.on('syncComplete', function (data) {
        console.log("syncComplete callback call data: " + data);
    });
    ```

### off<sup>8+</sup>

off(event:'dataChange', observer?: Callback&lt;ChangeNotification&gt;): void;

Unsubscribes from data change events. This method uses a synchronouscallback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| event  |'dataChange'  | Yes|Type of the events to unsubscribe from.|
| observer |Callback&lt;[ChangeNotification](#changenotificationa)&gt; |No|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    kvStore.on('dataChange', function (data) {
        console.log("syncComplete callback call data: " + data);
    });
    kvStore.off('dataChange', function (data) {
        console.log("syncComplete callback call data: " + data);
    });
    ```


### putBatch<sup>8+</sup>

putBatch(entries: Entry[], callback: AsyncCallback&lt;void&gt;): void;

Inserts KV pairs in batches to this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| entries  |[Entry](#entry)[] | Yes|KV pairs to insert in batches.|
| callback |Asyncallback&lt;void&gt; |Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            await kvStore.getEntries('batch_test_string_key', function (err,entrys) {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
            });
        });
    }catch(e) {
        console.log('PutBatch e ' + e);
    }
    
    ```


### putBatch<sup>8+</sup>

putBatch(entries: Entry[]): Promise&lt;void&gt;;

Inserts KV pairs in batches to this KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| entries  |[Entry](#entry)[] | Yes|KV pairs to insert in batches.|

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            await kvStore.getEntries('batch_test_string_key').then((entrys) => {
                console.log('getEntries success');
                console.log('PutBatch ' + JSON.stringify(entries));
            }).catch((err) => {
                console.log('getEntries fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('PutBatch e ' + e);
    }
    ```


### deleteBatch<sup>8+</sup>

deleteBatch(keys: string[], callback: AsyncCallback&lt;void&gt;): void;

Deletes KV pairs in batches from this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| keys  |string[] | Yes|KV pairs to delete in batches.|
| callback  |AsyncCallback&lt;void&gt; | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        let keys = [];
        for (var i = 0; i < 5; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
            keys.push(key + i);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            await kvStore.deleteBatch(keys, async function (err,data) {
                console.log('deleteBatch success');
            });
        });
    }catch(e) {
        console.log('DeleteBatch e ' + e);
    }
    ```


### deleteBatch<sup>8+</sup> ###

deleteBatch(keys: string[]): Promise&lt;void&gt;;

Deletes KV pairs in batches from this KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| keys   |string[] | Yes|KV pairs to delete in batches.|

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        let keys = [];
        for (var i = 0; i < 5; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
            keys.push(key + i);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            await kvStore.deleteBatch(keys).then((err) => {
                console.log('deleteBatch success');
            }).catch((err) => {
                console.log('deleteBatch fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('DeleteBatch e ' + e);
    }
    ```


### startTransaction<sup>8+</sup> ###

startTransaction(callback: AsyncCallback&lt;void&gt;): void;

Starts transactions in this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| callback  |AsyncCallback&lt;void&gt; | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    function putBatchString(len, prefix) {
        let entries = [];
        for (var i = 0; i < len; i++) {
            var entry = {
                key : prefix + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        return entries;
    }
    try {
        var count = 0;
        kvStore.on('dataChange', 0, function (data) {
            console.log('startTransaction 0' + data)
            count++;
        });
        kvStore.startTransaction(async function (err,data) {
            console.log('startTransaction success');
            let entries = putBatchString(10, 'batch_test_string_key');
            console.log('entries: ' + JSON.stringify(entries));
            await kvStore.putBatch(entries, async function (err,data) {
                console.log('putBatch success');
            });
        });
    }catch(e) {
        console.log('startTransaction e ' + e);
    }
    ```


### startTransaction<sup>8+</sup> ###

startTransaction(): Promise&lt;void&gt;;

Starts transactions in this KV store. This method uses a promise to return the result.

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        var count = 0;
        kvStore.on('dataChange', distributedData.SubscribeType.SUBSCRIBE_TYPE_ALL, function (data) {
            console.log('startTransaction ' + JSON.stringify(data));
            count++;
        });
        kvStore.startTransaction().then(async (err) => {
            console.log('startTransaction success');
        }).catch((err) => {
            console.log('startTransaction fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('startTransaction e ' + e);
    }
    ```


### commit<sup>8+</sup> ###

commit(callback: AsyncCallback&lt;void&gt;): void;

Commits transactions in this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| callback  |AsyncCallback&lt;void&gt; | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.commit(function (err,data) {
            if (err == undefined) {
                console.log('commit success');
            } else {
                console.log('commit fail');
            }
        });
    }catch(e) {
        console.log('Commit e ' + e);
    }
    ```


### commit<sup>8+</sup> ###

commit(): Promise&lt;void&gt;;

Commits transactions in this KV store. This method uses a promise to return the result.

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.commit().then(async (err) => {
            console.log('commit success');
        }).catch((err) => {
            console.log('commit fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('Commit e ' + e);
    }
    ```


### rollback<sup>8+</sup> ###

rollback(callback: AsyncCallback&lt;void&gt;): void;

Rolls back transactions in this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| callback  |AsyncCallback&lt;void&gt; | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.rollback(function (err,data) {
            if (err == undefined) {
                console.log('commit success');
            } else {
                console.log('commit fail');
            }
        });
    }catch(e) {
        console.log('Rollback e ' + e);
    }
    ```


### rollback<sup>8+</sup> ###

rollback(): Promise&lt;void&gt;;

Rolls back transactions in this KV store. This method uses a promise to return the result.

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.rollback().then(async (err) => {
            console.log('rollback success');
        }).catch((err) => {
            console.log('rollback fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('Rollback e ' + e);
    }
    ```


### enableSync<sup>8+</sup> ###

enableSync(enabled: boolean, callback: AsyncCallback&lt;void&gt;): void;

Sets data synchronization, which can be enabled or disable. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| enabled  |boolean | Yes|Whether to enable data synchronization. The value **true** means to enable data synchronization, and **false** means the opposite.|
| callback  |AsyncCallback&lt;void&gt; | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.enableSync(true, function (err,data) {
            if (err == undefined) {
                console.log('enableSync success');
            } else {
                console.log('enableSync fail');
            }
        });
    }catch(e) {
        console.log('EnableSync e ' + e);
    }
    ```


### enableSync<sup>8+</sup> ###

enableSync(enabled: boolean): Promise&lt;void&gt;;

Sets data synchronization, which can be enabled or disable. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| enabled  |boolean | Yes|Whether to enable data synchronization. The value **true** means to enable data synchronization, and **false** means the opposite.|

-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.enableSync(true).then((err) => {
            console.log('enableSync success');
        }).catch((err) => {
            console.log('enableSync fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('EnableSync e ' + e);
    }
    ```


### setSyncRange<sup>8+</sup> ###

setSyncRange(localLabels: string[], remoteSupportLabels: string[], callback: AsyncCallback&lt;void&gt;): void;

Sets the data synchronization range. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| localLabels  |string[] | Yes|Synchronization labels set for the local device.|
| remoteSupportLabels  |string[] | Yes|Synchronization labels set for remote devices.|
| callback  |AsyncCallback&lt;void&gt; | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        const localLabels = ['A', 'B'];
        const remoteSupportLabels = ['C', 'D'];
        kvStore.setSyncRange(localLabels, remoteSupportLabels, function (err,data) {
            console.log('SetSyncRange put success');
        });
    }catch(e) {
        console.log('SetSyncRange e ' + e);
    }
    ```


### setSyncRange<sup>8+</sup> ###

setSyncRange(localLabels: string[], remoteSupportLabels: string[]): Promise&lt;void&gt;;

Sets the data synchronization range. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| localLabels  |string[] | Yes|Synchronization labels set for the local device.|
| remoteSupportLabels  |string[] | Yes|Synchronization labels set for remote devices.|


-   Return value

| Type| Description|
| ------  | -------   |
| Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        const localLabels = ['A', 'B'];
        const remoteSupportLabels = ['C', 'D'];
        kvStore.setSyncRange(localLabels, remoteSupportLabels).then((err) => {
            console.log('setSyncRange success');
        }).catch((err) => {
            console.log('delete fail ' + err);
        });
    }catch(e) {
        console.log('SetSyncRange e ' + e);
    }
    ```


## SubscribeType

Defines the subscription type.

| Name| Default Value| Description|
| -----  | ------   | ----------------------- |
| SUBSCRIBE_TYPE_LOCAL  |0 |Local data changes.|
| SUBSCRIBE_TYPE_REMOTE |1 |Remote data changes.|
| SUBSCRIBE_TYPE_ALL  |2 |Local and remote data changes.|

## ChangeNotification

Defines the content of data change notifications, including inserted data, updated data, deleted data, and device ID.

| Name| Type|Readable|Writable| Description|
| ----- | -------   | -----| ------|------------------------ |
| insertEntries | [Entry](#entry)[]   | Yes|  Yes|Data inserted.|
| updateEntries | [Entry](#entry)[]   | Yes|  Yes|Data updated.|
| deleteEntries | [Entry](#entry)[]   | Yes|  Yes|Data deleted.|
| deviceId | string   | Yes|  Yes|UUID of the device.|

## Entry

Defines the KV pairs stored in the KV store.

| Name| Type|Readable|Writable| Description|
| ----- | -------   | -----| ------|------------------------ |
| key | string   | Yes|  Yes|Key of the KV pair stored in the KV store.|
| value | [Value](#value) | Yes|  Yes|Value of the KV pair stored in the KV store.|


## Value

Defines the value in a KV pair.

| Name| Type|Readable|Writable| Description|
| ----- | -------   | -----| ------|------------------------ |
| type | [ValueType](#value)   | Yes|  Yes|Type of the value.|
| value | Uint8Array / string / number / boolean| Yes|  Yes|Specific value.|

## ValueType

Enumerates the types of values in KV pairs.

These value types can be used only by internal applications.

| Name| Default Value| Description|
| -----  | ------   | ----------------------- |
| STRING  |0 |String.|
| INTEGER |1 |Integer.|
| FLOAT   |2 |Float (single-precision floating point).|
| BYTE_ARRAY   |3 |Byte array.|
| BOOLEAN   |4 |Boolean.|
| DOUBLE   |5 |Double (double-precision floating point).|

## SingleKVStore

Provides methods to query and synchronize data in a single KV store. This class inherits from **KVStore**. Before calling any method in **SingleKVStore**, you must use **getKVStore** to obtain a **SingleKVStore** object.

### get

get(key: string, callback: AsyncCallback&lt;Uint8Array | string | boolean | number&gt;): void

Obtains the value of a specified key. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| key    |string   | Yes|Key of the value to obtain. It cannot be empty, and the length cannot exceed [MAX\_KEY\_LENGTH](#constants).|
| callback  |AsyncCallback&lt;Uint8Array / string / boolean / number&gt;) | Yes|Callback used to return the value obtained.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-test-string';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, function (err,data) {
            if (err != undefined) {
                console.log("put err: " + JSON.stringify(err));
                return;
            }
            console.log("put success");
            kvStore.get(KEY_TEST_STRING_ELEMENT, function (err,data) {
                console.log("get success data: " + data);
            });
        });
    }catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```


### get

get(key: string): Promise&lt;Uint8Array | string | boolean | number&gt;

Obtains the value of a specified key. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| key    |string   | Yes|Key of the value to obtain. It cannot be empty, and the length cannot exceed [MAX\_KEY\_LENGTH](#constants).|


-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;Uint8Array / string / boolean / number&gt; |Promise used to return the value obtained.|


-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-test-string';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT).then((data) => {
            console.log("put success: " + JSON.stringify(data));
            kvStore.get(KEY_TEST_STRING_ELEMENT).then((data) => {
                console.log("get success data: " + data);
            }).catch((err) => {
                console.log("get err: " + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log("put err: " + JSON.stringify(err));
        });
    }catch (e) {
        console.log("An unexpected error occurred. Error:" + e);
    }
    ```

### getEntries<sup>8+</sup> ###

getEntries(keyPrefix: string, callback: AsyncCallback&lt;Entry[]&gt;): void;

Obtains the KV pairs that match the specified key prefix. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| keyPrefix    |string   | Yes|Key prefix to match.|
| callback    |AsyncCallback&lt;Entry[]&gt;   | Yes|Callback used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_number_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.INTEGER,
                    value : 222
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            await kvStore.getEntries('batch_test_number_key', function (err,entrys) {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
            });
        });
    }catch(e) {
        console.log('PutBatch e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(keyPrefix: string): Promise&lt;Entry[]&gt;;

Obtains the KV pairs that match the specified key prefix. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| keyPrefix    |string   | Yes|Key prefix to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[Entry](#entry)[]&gt; |Promise used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + entries);
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            await kvStore.getEntries('batch_test_string_key').then((entrys) => {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
                console.log('entrys[0].value: ' + JSON.stringify(entrys[0].value));
                console.log('entrys[0].value.value: ' + entrys[0].value.value);
            }).catch((err) => {
                console.log('getEntries fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('PutBatch e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(query: Query, callback: AsyncCallback&lt;Entry[]&gt;): void;

Obtains the KV pairs that match the specified **Query** object. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| query  |[Query](#querysup8sup)   | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;Entry[]&gt;   | Yes|Callback used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        var arr = new Uint8Array([21,31]);
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_bool_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.BYTE_ARRAY,
                    value : arr
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getEntries(query, function (err,entrys) {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
            });
        });
        console.log('GetEntries success');
    }catch(e) {
        console.log('GetEntries e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(query: Query): Promise&lt;Entry[]&gt;;

Obtains the KV pairs that match the specified **Query** object. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| query  |[Query](#querysup8sup)   | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[Entry](#entry)[]&gt; |Promise used to return the KV pairs obtained.|

-   Example

    ```
    try {
        var arr = new Uint8Array([21,31]);
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_bool_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.BYTE_ARRAY,
                    value : arr
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getEntries(query).then((entrys) => {
                console.log('getEntries success');
            }).catch((err) => {
                console.log('getEntries fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('GetEntries putBatch fail ' + JSON.stringify(err))
        });
        console.log('GetEntries success');
    }catch(e) {
        console.log('GetEntries e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(keyPrefix: string, callback: AsyncCallback&lt;KvStoreResultSet&gt;): void;

Obtains the result set with the specified key prefix from this single KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| keyPrefix  |string   | Yes|Key prefix to match.|
| callback  |AsyncCallback&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)&gt;   | Yes|Callback used to return the result set obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('GetResultSet putBatch success');
            await kvStore.getResultSet('batch_test_string_key', async function (err, result) {
                console.log('GetResultSet getResultSet success');
                resultSet = result;
                kvStore.closeResultSet(resultSet, function (err, data) {
                    console.log('GetResultSet closeResultSet success');
                })
            });
        });
    }catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(keyPrefix: string): Promise&lt;KvStoreResultSet&gt;;

Obtains the result set with the specified key prefix from this single KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------  | ----  | ----------------------- |
| keyPrefix  |string   | Yes|Key prefix to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)&gt; |Promise used to return the result set obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
        }).catch((err) => {
            console.log('PutBatch putBatch fail ' + JSON.stringify(err));
        });
        kvStore.getResultSet('batch_test_string_key').then((result) => {
            console.log('GetResult getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
        kvStore.closeResultSet(resultSet).then((err) => {
            console.log('GetResult closeResultSet success');
        }).catch((err) => {
            console.log('closeResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResult e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(query: Query, callback: AsyncCallback&lt;KvStoreResultSet&gt;): void;

Obtains the **KvStoreResultSet** object that matches the specified **Query** object. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |Query    | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)&gt;   | Yes|Callback used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getResultSet(query, async function (err, result) {
                console.log('getResultSet success');
                resultSet = result;
            });
        });
    } catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(query: Query): Promise&lt;KvStoreResultSet&gt;;

Obtains the **KvStoreResultSet** object that matches the specified **Query** object. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)    | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)&gt; |Promise used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
        const query = new distributedData.Query();
        query.prefixKey("batch_test");
        kvStore.getResultSet(query).then((result) => {
            console.log(' getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```

### closeResultSet<sup>8+</sup> ###

closeResultSet(resultSet: KvStoreResultSet, callback: AsyncCallback&lt;void&gt;): void;

Closes the **KvStoreResultSet** object obtained by **getResultSet**. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| resultSet  |[KvStoreResultSet](#kvstoreresultsetsup8sup)   | Yes|**KvStoreResultSet** object to close.|
| callback  |AsyncCallback&lt;void&gt;   | Yes|Callback used to return the execution result.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet = null;
        kvStore.closeResultSet(resultSet, function (err, data) {
            if (err == undefined) {
                console.log('closeResultSet success');
            } else {
                console.log('closeResultSet fail');
            }
        });
    }catch(e) {
        console.log('CloseResultSet e ' + e);
    }
    ```


### closeResultSet<sup>8+</sup> ###

closeResultSet(resultSet: KvStoreResultSet): Promise&lt;void&gt;;

Closes the **KvStoreResultSet** object obtained by **getResultSet**. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| resultSet  |[KvStoreResultSet](#kvstoreresultsetsup8sup)   | Yes|**KvStoreResultSet** object to close.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet = null;
        kvStore.closeResultSet(resultSet).then(() => {
            console.log('closeResultSet success');
        }).catch((err) => {
            console.log('closeResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('CloseResultSet e ' + e);
    }
    ```


### getResultSize<sup>8+</sup> ###

getResultSize(query: Query, callback: AsyncCallback&lt;number&gt;): void;

Obtains the number of results matching the specified **Query** object. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)   | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;number&gt;   | Yes|Callback used to return the number of results obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getResultSize(query, async function (err, resultSize) {
                console.log('getResultSet success');
            });
        });
    } catch(e) {
        console.log('GetResultSize e ' + e);
    }
    ```


### getResultSize<sup>8+</sup> ###

getResultSize(query: Query): Promise&lt;number&gt;;

Obtains the number of results matching the specified **Query** object. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)   | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;number&gt; |Promise used to return the number of results obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
        const query = new distributedData.Query();
        query.prefixKey("batch_test");
        kvStore.getResultSize(query).then((resultSize) => {
            console.log('getResultSet success');
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResultSize e ' + e);
    }
    ```


### removeDeviceData<sup>8+</sup> ###

removeDeviceData(deviceId: string, callback: AsyncCallback&lt;void&gt;): void;

Deletes data of a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string   | Yes|ID of the target device.|
| callback  |AsyncCallback&lt;void&gt;   | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string_2';
    const VALUE_TEST_STRING_ELEMENT = 'value-string-002';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, async function (err,data) {
            console.log('put success');
            const deviceid = 'no_exist_device_id';
            await kvStore.removeDeviceData(deviceid, async function (err,data) {
                if (err == undefined) {
                    console.log('removeDeviceData success');
                } else {
                    console.log('removeDeviceData fail');
                    await kvStore.get(KEY_TEST_STRING_ELEMENT, async function (err,data) {
                        console.log('RemoveDeviceData get success');
                    });
                }
            });
        });
    }catch(e) {
        console.log('RemoveDeviceData e ' + e);
    }
    ```


### removeDeviceData<sup>8+</sup> ###

removeDeviceData(deviceId: string): Promise&lt;void&gt;;

Deletes data of a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string   | Yes|ID of the target device.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string_2';
    const VALUE_TEST_STRING_ELEMENT = 'value-string-001';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT).then((err) => {
            console.log('removeDeviceData put success');
        }).catch((err) => {
            console.log('put fail ' + JSON.stringify(err));
        });
        const deviceid = 'no_exist_device_id';
        kvStore.removeDeviceData(deviceid).then((err) => {
            console.log('removeDeviceData success');
        }).catch((err) => {
            console.log('removeDeviceData fail ' + JSON.stringify(err));
        });
        kvStore.get(KEY_TEST_STRING_ELEMENT).then((data) => {
            console.log('get success data:' + data);
        }).catch((err) => {
            console.log('RemoveDeviceData get fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('RemoveDeviceData e ' + e);
    }
    ```


### on<sup>8+</sup> ###

on(event: 'syncComplete', syncCallback: Callback<Array&lt;[string, number]&gt;): void;

Subscribes to the synchronization completion events. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| event  |'syncComplete'   | Yes|Event triggered when the synchronization is complete.|
| syncCallback  |Callback<Array&lt;[string, number]&gt;   | Yes|Callback used to return the synchronization result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_FLOAT_ELEMENT = 'key_test_float';
    const VALUE_TEST_FLOAT_ELEMENT = 321.12;
    try {
        kvStore.on('syncComplete', function (data) {
            console.log('syncComplete ' + data)
        });
        kvStore.put(KEY_TEST_FLOAT_ELEMENT, VALUE_TEST_FLOAT_ELEMENT).then((data) => {
            console.log('syncComplete put success');
        }).catch((error) => {
            console.log('syncComplete put fail ' + error);
        });
    }catch(e) {
        console.log('syncComplete put e ' + e);
    }
    ```


### off<sup>8+</sup> ###

off(event: 'syncComplete', syncCallback?: Callback<Array&lt;[string, number]&gt;): void;

Unsubscribes from the synchronization completion events. This method uses a synchronization callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| event  |'syncComplete'   | Yes|Event triggered when the synchronization is complete.|
| syncCallback  |Callback<Array&lt;[string, number]&gt;   | No|Callback used to return the synchronization result.|


-   Example

    ```
    let kvStore;
    try {
        const func = function (data) {
            console.log('syncComplete ' + data)
        };
        kvStore.on('syncComplete', func);
        kvStore.off('syncComplete', func);
    }catch(e) {
        console.log('syncComplete e ' + e);
    }
    ```


### sync

sync(deviceIdList: string[], mode: SyncMode, allowedDelayMs?: number): void

Manually triggers KV store synchronization synchronously.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceIdList  |string[]  | Yes|IDs of the devices to be synchronized. These devices must be in the same networking environment.|
| mode  |[SyncMode](#syncmode)   | Yes|Data synchronization mode.|
| allowedDelayMs  |number   | No|Allowed synchronization delay time, in ms.|

-   Example

    ```
    let kvStore;
    kvStore.sync('deviceIds', distributedData.SyncMode.PULL_ONLY, 1000);
    ```

### setSyncParam<sup>8+</sup> ###

setSyncParam(defaultAllowedDelayMs: number, callback: AsyncCallback&lt;void&gt;): void;

Sets the default delay of database synchronization. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| defaultAllowedDelayMs  |number  | Yes|Default delay allowed for database synchronization, in ms.|
| callback  |AsyncCallback&lt;void&gt;  | Yes|Callback used to return the result.|


-   Example

    ```
    let kvStore;
    try {
        const defaultAllowedDelayMs = 500;
        kvStore.setSyncParam(defaultAllowedDelayMs, function (err,data) {
            console.log('SetSyncParam put success');
        });
    }catch(e) {
        console.log('testSingleKvStoreSetSyncParam e ' + e);
    }
    ```


### setSyncParam<sup>8+</sup> ###

setSyncParam(defaultAllowedDelayMs: number): Promise&lt;void&gt;;

Sets the default delay of database synchronization. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| defaultAllowedDelayMs  |number  | Yes|Default delay allowed for database synchronization, in ms.|


-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        const defaultAllowedDelayMs = 500;
        kvStore.setSyncParam(defaultAllowedDelayMs).then((err) => {
            console.log('SetSyncParam put success');
        }).catch((err) => {
            console.log('SetSyncParam put fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('SetSyncParam e ' + e);
    }
    ```


### getSecurityLevel<sup>8+</sup> ###

getSecurityLevel(callback: AsyncCallback&lt;SecurityLevel&gt;): void;

Obtains the security level of this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| callback  |AsyncCallback&lt;[SecurityLevel](#securitylevel)&gt;  | Yes|Callback used to return the security level obtained.|

-   Example

    ```
    let kvStore;
    try {
        kvStore.getSecurityLevel(function (err,data) {
            console.log('getSecurityLevel success');
        });
    }catch(e) {
        console.log('GetSecurityLeve e ' + e);
    }
    ```


### getSecurityLevel<sup>8+</sup> ###

getSecurityLevel(): Promise&lt;SecurityLevel&gt;;

Obtains the security level of this KV store. This method uses a promise to return the result.

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[SecurityLevel](#securitylevel)&gt; |Promise used to return the security level obtained.|


-   Example

    ```
    let kvStore;
    try {
        kvStore.getSecurityLevel().then((data) => {
            console.log(' getSecurityLevel success');
        }).catch((err) => {
            console.log('getSecurityLevel fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetSecurityLeve e ' + e);
    }
    ```


## DeviceKVStore<sup>8+</sup> ##

Provides methods to manage distributed data by device in the distributed system. This class inherits from **KvStore** and provides data query and synchronization methods. Before calling any method in **DeviceKVStore**, you must use **getKVStore** to obtain a **DeviceKVStore** object.

### get<sup>8+</sup> ###

get(deviceId: string, key: string, callback: AsyncCallback&lt;boolean|string|number|Uint8Array&gt;): void;

Obtains the string value that matches the specified key for a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| key       |string  | Yes|Key to match.|
| callback  |AsyncCallback&lt;boolean/string/number/Uint8Array&gt;  | Yes|Callback used to return the value obtained.|


-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string_2';
    const VALUE_TEST_STRING_ELEMENT = 'value-string-002';
    try{
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, async function (err,data) {
            console.log('put success');
            kvStore.get('localDeviceId', KEY_TEST_STRING_ELEMENT, function (err,data) {
                console.log('get success');
            });
        })
    }catch(e) {
        console.log('get e' + e);
    }
    ```


### get<sup>8+</sup> ###

get(deviceId: string, key: string): Promise&lt;boolean|string|number|Uint8Array&gt;;

Obtains the string value that matches the specified key for a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| key       |string  | Yes|Key to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;boolean/string/number/Uint8Array&gt; |Promise used to return the value obtained.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string_2';
    const VALUE_TEST_STRING_ELEMENT = 'value-string-002';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT).then(async (data) => {
            console.log(' put success');
            kvStore.get('localDeviceId', KEY_TEST_STRING_ELEMENT).then((data) => {
                console.log('get success');
            }).catch((err) => {
                console.log('get fail ' + JSON.stringify(err));
            });
        }).catch((error) => {
            console.log('put error' + error);
        });
    } catch (e) {
        console.log('Get e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(deviceId: string, keyPrefix: string, callback: AsyncCallback&lt;Entry[]&gt;): void;

Obtains the KV pairs that match the specified key prefix for a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| keyPrefix |string  | Yes|Key prefix to match.|
| callback  |AsyncCallback&lt;[Entry](#entry)[]&gt;  | Yes|Callback used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + entries);
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            await kvStore.getEntries('localDeviceId', 'batch_test_string_key', function (err,entrys) {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
            });
        });
    }catch(e) {
        console.log('PutBatch e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(deviceId: string, keyPrefix: string): Promise&lt;Entry[]&gt;;

Obtains the KV pairs that match the specified key prefix for a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| keyPrefix |string  | Yes|Key prefix to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[Entry](#entry)[]&gt; |Promise used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + entries);
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            await kvStore.getEntries('localDeviceId', 'batch_test_string_key').then((entrys) => {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
                console.log('entrys[0].value: ' + JSON.stringify(entrys[0].value));
                console.log('entrys[0].value.value: ' + entrys[0].value.value);
            }).catch((err) => {
                console.log('getEntries fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('PutBatch e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(query: Query, callback: AsyncCallback&lt;Entry[]&gt;): void;

Obtains the KV pairs matching the specified **Query** object. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|
| callback |AsyncCallback&lt;[Entry](#entry)[]&gt;  | Yes|Callback used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        var arr = new Uint8Array([21,31]);
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_bool_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.BYTE_ARRAY,
                    value : arr
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            expect(err == undefined).assertTrue();
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            query.deviceId('localDeviceId');
            await kvStore.getEntries(query, function (err,entrys) {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
            });
        });
        console.log('GetEntries success');
    }catch(e) {
        console.log('GetEntries e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(query: Query): Promise&lt;Entry[]&gt;;

Obtains the KV pairs matching the specified **Query** object. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[Entry](#entry)[]&gt; |Promise used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        var arr = new Uint8Array([21,31]);
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_bool_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.BYTE_ARRAY,
                    value : arr
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getEntries(query).then((entrys) => {
                console.log('getEntries success');
            }).catch((err) => {
                console.log('getEntries fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('GetEntries putBatch fail ' + JSON.stringify(err))
        });
        console.log('GetEntries success');
    }catch(e) {
        console.log('GetEntries e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(deviceId: string, query: Query, callback: AsyncCallback&lt;Entry[]&gt;): void;

Obtains the KV pairs matching the specified **Query** object for a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|
| callback |AsyncCallback&lt;[Entry](#entry)[]&gt;  | Yes|Callback used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        var arr = new Uint8Array([21,31]);
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_bool_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.BYTE_ARRAY,
                    value : arr
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries, async function (err,data) {
            console.log('putBatch success');
            expect(err == undefined).assertTrue();
            var query = new distributedData.Query();
            query.deviceId('localDeviceId');
            query.prefixKey("batch_test");
            await kvStore.getEntries('localDeviceId', query, function (err,entrys) {
                console.log('getEntries success');
                console.log('entrys.length: ' + entrys.length);
                console.log('entrys[0]: ' + JSON.stringify(entrys[0]));
            })
        });
        console.log('GetEntries success');
    }catch(e) {
        console.log('GetEntries e ' + e);
    }
    ```


### getEntries<sup>8+</sup> ###

getEntries(deviceId: string, query: Query): Promise&lt;Entry[]&gt;;

Obtains the KV pairs matching the specified **Query** object for a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[Entry](#entry)[]&gt; |Promise used to return the KV pairs obtained.|

-   Example

    ```
    let kvStore;
    try {
        var arr = new Uint8Array([21,31]);
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_bool_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.BYTE_ARRAY,
                    value : arr
                }
            }
            entries.push(entry);
        }
        console.log('entries: ' + JSON.stringify(entries));
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
            var query = new distributedData.Query();
            query.deviceId('localDeviceId');
            query.prefixKey("batch_test");
            await kvStore.getEntries('localDeviceId', query).then((entrys) => {
                console.log('getEntries success');
            }).catch((err) => {
                console.log('getEntries fail ' + JSON.stringify(err));
            });
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
        console.log('GetEntries success');
    }catch(e) {
        console.log('GetEntries e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(deviceId: string, keyPrefix: string, callback: AsyncCallback&lt;KvStoreResultSet&gt;): void;

Obtains the **KvStoreResultSet** object that matches the specified key prefix for a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| keyPrefix |string  | Yes|Key prefix to match.|
| callback  |AsyncCallback&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)[]&gt;  | Yes|Callback used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        kvStore.getResultSet('localDeviceId', 'batch_test_string_key', async function (err, result) {
            console.log('getResultSet success');
            resultSet = result;
            await kvStore.closeResultSet(resultSet, function (err, data) {
                console.log('closeResultSet success');
            })
        });
    }catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(deviceId: string, keyPrefix: string): Promise&lt;KvStoreResultSet&gt;;

Obtains the **KvStoreResultSet** object that matches the specified key prefix for a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| keyPrefix |string  | Yes|Key prefix to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)[]&gt; |Promise used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        kvStore.getResultSet('localDeviceId', 'batch_test_string_key').then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
        kvStore.closeResultSet(resultSet).then((err) => {
            console.log('closeResultSet success');
        }).catch((err) => {
            console.log('closeResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(query: Query, callback: AsyncCallback&lt;KvStoreResultSet&gt;): void;

Obtains the **KvStoreResultSet** object that matches the specified **Query** object. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)[]&gt;  | Yes|Callback used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            query.deviceId('localDeviceId');
            await kvStore.getResultSet(query, async function (err, result) {
                console.log('getResultSet success');
                resultSet = result;
                await kvStore.closeResultSet(resultSet, function (err, data) {
                    console.log('closeResultSet success');
                })
            });
        });
    } catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(query: Query): Promise&lt;KvStoreResultSet&gt;;

Obtains the **KvStoreResultSet** object that matches the specified **Query** object. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)[]&gt; |Promise used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
        }).catch((err) => {
            console.log('putBatch fail ' + err);
        });
        const query = new distributedData.Query();
        query.deviceId('localDeviceId');
        query.prefixKey("batch_test");
        console.log("GetResultSet " + query.getSqlLike());
        kvStore.getResultSet(query).then((result) => {
            console.log('getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
        kvStore.closeResultSet(resultSet).then((err) => {
            console.log('closeResultSet success');
        }).catch((err) => {
            console.log('closeResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(deviceId: string, query: Query, callback: AsyncCallback&lt;KvStoreResultSet&gt;): void;

Obtains the **KvStoreResultSet** object that matches the specified **Query** object for a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)[]&gt;  | Yes|Callback used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getResultSet('localDeviceId', query, async function (err, result) {
                console.log('getResultSet success');
                resultSet = result;
                await kvStore.closeResultSet(resultSet, function (err, data) {
                    console.log('closeResultSet success');
                })
            });
        });
    } catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### getResultSet<sup>8+</sup> ###

getResultSet(deviceId: string, query: Query): Promise&lt;KvStoreResultSet&gt;;

Obtains the **KvStoreResultSet** object that matches the specified **Query** object for a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|
| query  |[Query](#querysup8sup)  | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;[KvStoreResultSet](#kvstoreresultsetsup8sup)[]&gt; |Promise used to return the **KvStoreResultSet** object obtained.|

-   Example

    ```
    let kvStore;
    try {
        let resultSet;
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('GetResultSet putBatch success');
        }).catch((err) => {
            console.log('PutBatch putBatch fail ' + JSON.stringify(err));
        });
        const query = new distributedData.Query();
        query.prefixKey("batch_test");
        kvStore.getResultSet('localDeviceId', query).then((result) => {
            console.log('GetResultSet getResultSet success');
            resultSet = result;
        }).catch((err) => {
            console.log('GetResultSet getResultSet fail ' + JSON.stringify(err));
        });
        query.deviceId('localDeviceId');
        console.log("GetResultSet " + query.getSqlLike());
        kvStore.closeResultSet(resultSet).then((err) => {
            console.log('GetResultSet closeResultSet success');
        }).catch((err) => {
            console.log('GetResultSet closeResultSet fail ' + JSON.stringify(err));
        });
    
    }catch(e) {
        console.log('GetResultSet e ' + e);
    }
    ```


### closeResultSet<sup>8+</sup> ###

closeResultSet(resultSet: KvStoreResultSet, callback: AsyncCallback&lt;void&gt;): void;

Closes the **KvStoreResultSet** object obtained by **getResultSet**. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| resultSet  |[KvStoreResultSet](#getresultsetsup8sup)  | Yes|**KvStoreResultSet** object to close.|
| callback   |AsyncCallback&lt;void&gt;                 | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        console.log('CloseResultSet success');
        let resultSet = null;
        kvStore.closeResultSet(resultSet, function (err, data) {
            if (err == undefined) {
                console.log('closeResultSet success');
            } else {
                console.log('closeResultSet fail');
            }
        });
    }catch(e) {
        console.log('CloseResultSet e ' + e);
    }
    ```


### closeResultSet<sup>8+</sup> ###

closeResultSet(resultSet: KvStoreResultSet): Promise&lt;void&gt;;

Closes the **KvStoreResultSet** object obtained by **getResultSet**. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| resultSet  |[KvStoreResultSet](#getresultsetsup8sup)  | Yes|**KvStoreResultSet** object to close.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    try {
        console.log('CloseResultSet success');
        let resultSet = null;
        kvStore.closeResultSet(resultSet).then(() => {
            console.log('closeResultSet success');
        }).catch((err) => {
            console.log('closeResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('CloseResultSet e ' + e);
    }
    ```


### getResultSize<sup>8+</sup> ###

getResultSize(query: Query, callback: AsyncCallback&lt;number&gt;): void;

Obtains the number of results that matches the specified **Query** object. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query     |[Query](#querysup8sup)       | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;number&gt;  | Yes|Callback used to return the number of results obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            query.deviceId('localDeviceId');
            await kvStore.getResultSize(query, async function (err, resultSize) {
                console.log('getResultSet success');
            });
        });
    } catch(e) {
        console.log('GetResultSize e ' + e);
    }
    ```


### getResultSize<sup>8+</sup> ###

getResultSize(query: Query): Promise&lt;number&gt;;

Obtains the number of results that matches the specified **Query** object. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| query     |[Query](#querysup8sup)       | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;number&gt; |Promise used to return the number of results obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
        const query = new distributedData.Query();
        query.prefixKey("batch_test");
        query.deviceId('localDeviceId');
        kvStore.getResultSize(query).then((resultSize) => {
            console.log('getResultSet success');
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResultSize e ' + e);
    }
    ```


### getResultSize<sup>8+</sup> ###

getResultSize(deviceId: string, query: Query, callback: AsyncCallback&lt;number&gt;): void;

Obtains the number of results that matches the specified **Query** object for a device. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string                       | Yes|ID of the target device.|
| query     |[Query](#querysup8sup)       | Yes|**Query** object to match.|
| callback  |AsyncCallback&lt;number&gt;  | Yes|Callback used to return the number of results obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries, async function (err, data) {
            console.log('putBatch success');
            const query = new distributedData.Query();
            query.prefixKey("batch_test");
            await kvStore.getResultSize('localDeviceId', query, async function (err, resultSize) {
                console.log('getResultSet success');
            });
        });
    } catch(e) {
        console.log('GetResultSize e ' + e);
    }
    ```


### getResultSize<sup>8+</sup> ###

getResultSize(deviceId: string, query: Query): Promise&lt;number&gt;;

Obtains the number of results that matches the specified **Query** object for a device. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string                       | Yes|ID of the target device.|
| query     |[Query](#querysup8sup)       | Yes|**Query** object to match.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;number&gt; |Promise used to return the number of results obtained.|

-   Example

    ```
    let kvStore;
    try {
        let entries = [];
        for (var i = 0; i < 10; i++) {
            var key = 'batch_test_string_key';
            var entry = {
                key : key + i,
                value : {
                    type : distributedData.ValueType.STRING,
                    value : 'batch_test_string_value'
                }
            }
            entries.push(entry);
        }
        kvStore.putBatch(entries).then(async (err) => {
            console.log('putBatch success');
        }).catch((err) => {
            console.log('putBatch fail ' + JSON.stringify(err));
        });
        var query = new distributedData.Query();
        query.prefixKey("batch_test");
        kvStore.getResultSize('localDeviceId', query).then((resultSize) => {
            console.log('getResultSet success');
        }).catch((err) => {
            console.log('getResultSet fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('GetResultSize e ' + e);
    }
    ```


### removeDeviceData<sup>8+</sup> ###

removeDeviceData(deviceId: string, callback: AsyncCallback&lt;void&gt;): void;

Removes data of a device from this KV store. This method uses an asynchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string                       | Yes|ID of the target device.|
| callback  |AsyncCallback&lt;void&gt;    | Yes|Callback used to return the result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-string-001';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT, async function (err,data) {
            console.log('RemoveDeviceData  put success');
            const deviceid = 'no_exist_device_id';
            await kvStore.removeDeviceData(deviceid, async function (err,data) {
                if (err == undefined) {
                    console.log('removeDeviceData success');
                } else {
                    console.log('removeDeviceData fail');
                    await kvStore.get('localDeviceId', KEY_TEST_STRING_ELEMENT, async function (err,data) {
                        console.log('RemoveDeviceData get success');
                    });
                }
            });
        });
    }catch(e) {
        console.log('RemoveDeviceData e ' + e);
    }
    ```


### removeDeviceData<sup>8+</sup> ###

removeDeviceData(deviceId: string): Promise&lt;void&gt;;

Removes data of a device from this KV store. This method uses a promise to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceId  |string  | Yes|ID of the target device.|

-   Return value

| Type| Description|
| ------  | -------   |
|Promise&lt;void&gt; |Promise used to return the result.|

-   Example

    ```
    let kvStore;
    const KEY_TEST_STRING_ELEMENT = 'key_test_string';
    const VALUE_TEST_STRING_ELEMENT = 'value-string-001';
    try {
        kvStore.put(KEY_TEST_STRING_ELEMENT, VALUE_TEST_STRING_ELEMENT).then((err) => {
            console.log('RemoveDeviceData put success');
        }).catch((err) => {
            console.log('RemoveDeviceData put fail ' + JSON.stringify(err));
        });
        const deviceid = 'no_exist_device_id';
        kvStore.removeDeviceData(deviceid).then((err) => {
            console.log('removeDeviceData success');
        }).catch((err) => {
            console.log('removeDeviceData fail ' + JSON.stringify(err));
        });
        kvStore.get('localDeviceId', KEY_TEST_STRING_ELEMENT).then((data) => {
            console.log('RemoveDeviceData get success data:' + data);
        }).catch((err) => {
            console.log('RemoveDeviceData get fail ' + JSON.stringify(err));
        });
    }catch(e) {
        console.log('RemoveDeviceData e ' + e);
    }
    ```


### sync<sup>8+</sup> ###

sync(deviceIdList: string[], mode: SyncMode, allowedDelayMs?: number): void;

Manually triggers KV store synchronization synchronously.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| deviceIdList    |string[]               | Yes|IDs of the devices to be synchronized.|
| mode            |[SyncMode](#syncmode)  | Yes|Data synchronization mode, which can be **PUSH**, **PULL**, or **PUSH_PULL**.|
| allowedDelayMs  |number                 | No|Allowed synchronization delay time, in ms.|


-   Example

    ```
    let kvStore;
    const KEY_TEST_SYNC_ELEMENT = 'key_test_sync';
    const VALUE_TEST_SYNC_ELEMENT = 'value-string-001';
    try {
        kvStore.on('syncComplete', function (data) {
            console.log('Sync dataChange');
        });
        kvStore.put(KEY_TEST_SYNC_ELEMENT + 'testSync101', VALUE_TEST_SYNC_ELEMENT, function (err,data) {
            console.log('Sync put success');
            const devices = ['deviceList'];
            const mode = distributedData.SyncMode.PULL_ONLY;
            kvStore.sync(devices, mode);
        });
    }catch(e) {
        console.log('Sync e' + e);
    }
    ```

### on<sup>8+</sup> ###

on(event: 'syncComplete', syncCallback: Callback<Arrary&lt;<[string, number]&gt;): void;

Subscribes to the synchronization completion events. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| event    |'syncComplete'      | Yes|Event triggered when the synchronization is complete.|
| syncCallback            |Callback<Arrary&lt;<[string, number]&gt; | Yes|Callback used to return the synchronization result.|

-   Example
    ```
    const KEY_TEST_FLOAT_ELEMENT = 'key_test_float';
    const VALUE_TEST_FLOAT_ELEMENT = 321.12;
    try {
        kvStore.on('syncComplete', function (data) {
            console.log('syncComplete ' + data)
        });
        kvStore.put(KEY_TEST_FLOAT_ELEMENT, VALUE_TEST_FLOAT_ELEMENT).then((data) => {
            console.log('syncComplete put success');
        }).catch((error) => {
            console.log('syncComplete put fail ' + error);
        });
    }catch(e) {
        console.log('syncComplete put e ' + e);
    }
    ```


### off<sup>8+</sup> ###

off(event: 'syncComplete', syncCallback?: Callback<Array&lt;[string, number]&gt;): void;

Unsubscribes from the synchronization completion events. This method uses a synchronous callback to return the result.

-   Parameters

| Name| Type| Mandatory| Description|
| -----  | ------   | ----  | ----------------------- |
| event         |'syncComplete'                           | Yes|Event triggered when the synchronization is complete.|
| syncCallback  |Callback<Arrary&lt;<[string, number]&gt; | No|Callback used to return the synchronization result.|


-   Example

    ```
    let kvStore;
    try {
        const func = function (data) {
            console.log('syncComplete ' + data)
        };
        kvStore.on('syncComplete', func);
        kvStore.off('syncComplete', func);
    }catch(e) {
        console.log('syncComplete e ' + e);
    }
    ```


## SyncMode

Defines the synchronization mode.

| Name| Default Value| Description|
| -----      | ------    | ----------------------- |
| PULL_ONLY  |0          |Pull data from the peer end to the local end only.|
| PUSH_ONLY  |1          |Push data from the local end to the peer end only.|
| PUSH_PULL  |2          |Push data from the local end to the peer end and then pull data from the peer end to the local end.|