update docs

Signed-off-by: NAnnie_wang <annie.wangli@huawei.com>

en/application-dev/database/database-preference-guidelines.md

@@ -24,7 +24,7 @@ Obtain a **Preferences** instance for data operations. A **Preferences** instanc
 
 **Table 1** API for obtaining a **Preferences** instance
 
-| Package                 | API                                                      | Description                                                        |
+| Bundle Name           | API                                                      | Description                                                        |
 | --------------------- | ------------------------------------------------------------ | ------------------------------------------------------------ |
 | ohos.data.preferences | getPreferences(context: Context, name: string): Promise\<Preferences> | Obtains a **Preferences** instance.|
 
@@ -75,7 +75,7 @@ You can use the following APIs to delete a **Preferences** instance or data file
 
 **Table 6** APIs for deleting **Preferences**
 
-| Package                 | API                                                      | Description                                                        |
+| Bundle Name           | API                                                      | Description                                                        |
 | --------------------- | ------------------------------------------------------------ | ------------------------------------------------------------ |
 | ohos.data.preferences | deletePreferences(context: Context, name: string): Promise\<void> | Deletes a **Preferences** instance from the memory and its files from the device.|
 | ohos.data.preferences | removePreferencesFromCache(context: Context, name: string): Promise\<void> | Removes a **Preferences** instance from the memory to release memory.   |
@@ -113,22 +113,20 @@ You can use the following APIs to delete a **Preferences** instance or data file
 
    ```ts
    // Obtain the context.
-   import UIAbility from '@ohos.app.ability.UIAbility'
-   let context = null;
+   import UIAbility from '@ohos.app.ability.UIAbility';
    let preferences = null;
    export default class EntryAbility extends UIAbility {
-       onWindowStageCreate(windowStage){
-           context = this.context;
+       onWindowStageCreate(windowStage) {
+           let promise = data_preferences.getPreferences(this.context, 'mystore');
+            promise.then((pref) => {
+                preferences = pref;
+            }).catch((err) => {
+                console.info("Failed to get the preferences.");
+            })
        }
    }
    
-   let promise = data_preferences.getPreferences(context, 'mystore');
    
-   promise.then((pref) => {
-       preferences = pref;
-   }).catch((err) => {
-       console.info("Failed to get the preferences.");
-   })
    ```
 
 3. Write data.
@@ -200,6 +198,6 @@ You can use the following APIs to delete a **Preferences** instance or data file
    proDelete.then(() => {
         console.info("Deleted data successfully.");
    }).catch((err) => {
-       console.info("Failed to delete data. Cause: " + err);
+        console.info("Failed to delete data. Cause: " + err);
    })
    ```

en/application-dev/reference/apis/js-apis-data-preferences.md

@@ -22,8 +22,8 @@ import data_preferences from '@ohos.data.preferences';
 
 | Name            | Type| Readable| Writable| Description                                   |
 | ---------------- | -------- | ---- | ---- | --------------------------------------- |
-| MAX_KEY_LENGTH   | number   | Yes  | No  | Maximum length of a key. The key must be less than 80 bytes.    |
-| MAX_VALUE_LENGTH | number   | Yes  | No  | Maximum length of a value. The value must be less than 8192 bytes.|
+| MAX_KEY_LENGTH   | number   | Yes  | No  | Maximum length of a key. The maximum key length is 80 bytes.    |
+| MAX_VALUE_LENGTH | number   | Yes  | No  | Maximum length of a value. The maximum value length is 8192 bytes.|
 
 
 ## data_preferences.getPreferences