update docs

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

en/application-dev/reference/apis/Readme-EN.md

@@ -122,7 +122,7 @@
     - continuation
       - [continuationExtraParams](js-apis-continuation-continuationExtraParams.md)
       - [continuationResult](js-apis-continuation-continuationResult.md)
-  
+
 - Common Event and Notification
   - [@ohos.commonEventManager (Common Event) (Recommended)](js-apis-commonEventManager.md)
   - [@ohos.events.emitter (Emitter)](js-apis-emitter.md)
@@ -203,7 +203,6 @@
   - [@system.cipher (Cipher Algorithm)](js-apis-system-cipher.md)
   - security
     - [PermissionRequestResult](js-apis-permissionrequestresult.md)
-
 - Data Management
   - [@ohos.data.dataAbility (DataAbility Predicates)](js-apis-data-ability.md)
   - [@ohos.data.dataShare (DataShare)](js-apis-data-dataShare.md)
@@ -215,11 +214,15 @@
   - [@ohos.data.relationalStore (RDB Store)](js-apis-data-relationalStore.md)
   - [@ohos.data.ValuesBucket (Value Bucket)](js-apis-data-valuesBucket.md)
   - data/rdb
-    - [resultSet](js-apis-data-resultset.md)
+    - [resultSet (Result Set)](js-apis-data-resultset.md)
 - File Management
-  - [@ohos.environment](js-apis-environment.md)
+  - [@ohos.file.environment (Directory Environment Capability)](js-apis-file-environment.md)
   - [@ohos.file.fileAccess (User File Access and Management)](js-apis-fileAccess.md)
   - [@ohos.file.fileExtensionInfo (User File Extension Information)](js-apis-fileExtensionInfo.md)
+  - [@ohos.file.fs (File Management)](js-apis-file-fs.md)
+  - [@ohos.file.hash (File Hash Processing)](js-apis-file-hash.md)
+  - [@ohos.file.securityLabel (Data Label)](js-apis-file-securityLabel.md)
+  - [@ohos.file.statvfs (File System Space Statistics)](js-apis-file-statvfs.md)
   - [@ohos.filemanagement.userFileManager (User Data Management)](js-apis-userFileManager.md)
   - [@ohos.multimedia.medialibrary (Media Library Management)](js-apis-medialibrary.md)
   - [@ohos.storageStatistics (Application Storage Statistics)](js-apis-storage-statistics.md)

en/application-dev/reference/apis/js-apis-environment.md → en/application-dev/reference/apis/js-apis-file-environment.md

-# @ohos.environment (Directory Environment Capability)
+# @ohos.file.environment (Directory Environment Capability)
 
 The **Environment** module provides APIs for obtaining the root directories of the storage and public files.
 
 > **NOTE**
 >
-> - The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version.
+> - The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.
 > - The APIs of this module are system APIs and cannot be called by third-party applications.
+> - The APIs of this module support processing of error codes. For details, see [File Management Error Codes](../errorcodes/errorcode-filemanagement.md).
 
 ## Modules to Import
 
 ```js
-import environment from '@ohos.environment';
+import environment from '@ohos.file.environment';
 ```
 
 ## environment.getStorageDataDir
@@ -30,10 +31,10 @@ Obtains the root directory of the storage. This API uses a promise to return the
 **Example**
 
   ```js
-  environment.getStorageDataDir().then(function(path){
-      console.info("getStorageDataDir successfully:"+ path);
-  }).catch(function(error){
-      console.info("getStorageDataDir failed with error:"+ error);
+  environment.getStorageDataDir().then((path) => {
+      console.info("getStorageDataDir successfully, Path: " + path);
+  }).catch((err) => {
+      console.info("getStorageDataDir failed with error message: " + err.message + ", error code: " + err.code);
   });
   ```
 
@@ -54,8 +55,12 @@ Obtains the root directory of the storage. This API uses an asynchronous callbac
 **Example**
 
   ```js
-  environment.getStorageDataDir(function(error, path){
-      // do something
+  environment.getStorageDataDir((err, path) => {
+    if (err) {
+      console.info("getStorageDataDir failed with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.info("getStorageDataDir successfully, Path: " + path);
+    }
   });
   ```
 
@@ -76,10 +81,10 @@ Obtains the root directory of public files. This API uses a promise to return th
 **Example**
 
   ```js
-  environment.getUserDataDir().then(function(path){
-      console.info("getUserDataDir successfully:"+ path);
-  }).catch(function(error){
-      console.info("getUserDataDir failed with error:"+ error);
+  environment.getUserDataDir().then((path) => {
+    console.info("getUserDataDir successfully, Path: " + path);
+  }).catch((err) => {
+    console.info("getUserDataDir failed with error message: " + err.message + ", error code: " + err.code);
   });
   ```
 
@@ -100,7 +105,11 @@ Obtains the root directory of public files. This API uses an asynchronous callba
 **Example**
 
   ```js
-  environment.getUserDataDir(function(error, path){
-      // do something
+  environment.getUserDataDir((err, path) => {
+    if (err) {
+      console.info("getUserDataDir failed with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.info("getUserDataDir successfully, Path: " + path);
+    }
   });
   ```

en/application-dev/reference/apis/js-apis-file-hash.md

+# @ohos.file.hash (File Hash Processing)
+
+The **fileHash** module implements hash processing on files.
+
+> **NOTE**
+>
+> - The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.
+> - The APIs of this module support processing of error codes. For details, see [File Management Error Codes](../errorcodes/errorcode-filemanagement.md).
+
+## Modules to Import
+
+```js
+import Hash from '@ohos.file.hash';
+```
+
+## Guidelines
+
+Before using the APIs provided by this module to perform operations on a file or directory, obtain the path of the file or directory in the application sandbox as follows:
+
+**Stage Model**
+
+ ```js
+import UIAbility from '@ohos.app.ability.UIAbility';
+
+export default class EntryAbility extends UIAbility {
+    onWindowStageCreate(windowStage) {
+        let context = this.context;
+        let pathDir = context.filesDir;
+    }
+}
+ ```
+
+**FA Model**
+
+ ```js
+ import featureAbility from '@ohos.ability.featureAbility';
+ 
+ let context = featureAbility.getContext();
+ context.getFilesDir().then((data) => {
+      let pathDir = data;
+ })
+ ```
+
+For details about how to obtain the FA model context, see [Context](js-apis-inner-app-context.md#context).
+
+## Hash.hash
+
+hash(path: string, algorithm: string): Promise<string>
+
+Calculates a hash value for a file. This API uses a promise to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name   | Type  | Mandatory| Description                                                        |
+| --------- | ------ | ---- | ------------------------------------------------------------ |
+| path      | string | Yes  | Path of the file in the application sandbox.                            |
+| algorithm | string | Yes  | Algorithm used to calculate the hash value. The value can be **md5**, **sha1**, or **sha256**. **sha256** is recommended for security purposes.|
+
+**Return value**
+
+| Type                   | Description                        |
+| --------------------- | -------------------------- |
+| Promise<string> | Promise used to return the hash value. The hash value is a hexadecimal string consisting of digits and uppercase letters.|
+
+**Example**
+
+  ```js
+  let filePath = pathDir + "/test.txt";
+  Hash.hash(filePath, "sha256").then((str) => {
+    console.info("calculate file hash succeed:" + str);
+  }).catch((err) => {
+    console.info("calculate file hash failed with error message: " + err.message + ", error code: " + err.code);
+  });
+  ```
+
+## Hash.hash
+
+hash(path: string, algorithm: string, callback: AsyncCallback<string>): void
+
+Calculates a hash value for a file. This API uses an asynchronous callback to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name   | Type                       | Mandatory| Description                                                        |
+| --------- | --------------------------- | ---- | ------------------------------------------------------------ |
+| path      | string                      | Yes  | Path of the file in the application sandbox.                            |
+| algorithm | string                      | Yes  | Algorithm used to calculate the hash value. The value can be **md5**, **sha1**, or **sha256**. **sha256** is recommended for security purposes.|
+| callback  | AsyncCallback<string> | Yes  | Callback used to return the hash value obtained. The hash value is a hexadecimal string consisting of digits and uppercase letters.|
+
+**Example**
+  ```js
+  Hash.hash(filePath, "sha256", (err, str) => {
+    if (err) {
+      console.info("calculate file hash failed with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.info("calculate file hash succeed:" + str);
+    }
+  });
+  ```

en/application-dev/reference/apis/js-apis-file-securityLabel.md

+# @ohos.file.securityLabel (Data Label)
+
+The **securityLabel** module provides APIs for managing data security levels of files, including obtaining and setting file security levels.
+
+> **NOTE**
+>
+> - The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.
+>- The APIs of this module support processing of error codes. For details, see [File Management Error Codes](../errorcodes/errorcode-filemanagement.md).
+
+## Modules to Import
+
+```js
+import securityLabel from '@ohos.file.securityLabel';
+```
+
+## Guidelines
+
+Before using the APIs provided by this module to perform operations on files or directories, obtain the path of the file or directory in the application sandbox as follows:
+
+**Stage Model**
+
+ ```js
+import UIAbility from '@ohos.app.ability.UIAbility';
+
+export default class EntryAbility extends UIAbility {
+    onWindowStageCreate(windowStage) {
+        let context = this.context;
+        let pathDir = context.filesDir;
+    }
+}
+ ```
+
+**FA Model**
+
+ ```js
+ import featureAbility from '@ohos.ability.featureAbility';
+ 
+ let context = featureAbility.getContext();
+ context.getFilesDir().then((data) => {
+      let pathDir = data;
+ })
+ ```
+
+For details about how to obtain the FA model context, see [Context](js-apis-inner-app-context.md#context).
+
+## securityLabel.setSecurityLabel
+
+setSecurityLabel(path:string, type:dataLevel):Promise<void>
+
+Sets a security label for a file in asynchronous mode. This API uses a promise to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name   | Type      | Mandatory| Description                                        |
+| --------- | ------    | ---- | -------------------------------------------- |
+| path      | string    | Yes  | Path of the target file.                                    |
+| type      | dataLevel | Yes  | File security level to set, which can be **s0**, **s1**, **s2**, **s3**, or **s4**.|
+
+**Return value**
+
+| Type               | Description            |
+| ------------------- | ---------------- |
+| Promise<void> | Promise that returns no value.|
+
+**Example**
+
+  ```js
+  securityLabel.setSecurityLabel(path, "s0").then(() => {
+      console.info("setSecurityLabel successfully");
+  }).catch((err) => {
+      console.info("setSecurityLabel failed with error message: " + err.message + ", error code: " + err.code);
+  });
+  ```
+
+## securityLabel.setSecurityLabel
+
+setSecurityLabel(path:string, type:dataLevel, callback: AsyncCallback<void>):void
+
+Sets a security label for a file in asynchronous mode. This API uses an asynchronous callback to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name   | Type                     | Mandatory| Description                                        |
+| --------- | ------------------------- | ---- | -------------------------------------------- |
+| path      | string                    | Yes  | Path of the target file.                                    |
+| type      | dataLevel                 | Yes  | File security level to set, which can be **s0**, **s1**, **s2**, **s3**, or **s4**.|
+| callback  | AsyncCallback<void> | Yes  | Callback invoked to return the result.                  |
+
+**Example**
+
+  ```js
+  securityLabel.setSecurityLabel(path, "s0", (err) => {
+    if (err) {
+      console.info("setSecurityLabel failed with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.info("setSecurityLabel successfully.");
+    }
+  });
+  ```
+
+## securityLabel.setSecurityLabelSync
+
+setSecurityLabelSync(path:string, type:dataLevel):void
+
+Sets a security label for a file in synchronous mode.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name   | Type  | Mandatory| Description                                        |
+| --------- | ------ | ---- | -------------------------------------------- |
+| path      | string | Yes  | Path of the target file.                                    |
+| type      | dataLevel | Yes  | File security level to set, which can be **s0**, **s1**, **s2**, **s3**, or **s4**.|
+
+**Example**
+
+```js
+securityLabel.setSecurityLabelSync(path, "s0");
+```
+
+## securityLabel.getSecurityLabel
+
+getSecurityLabel(path:string):Promise<string>
+
+Obtains the security label of a file in asynchronous mode. This API uses a promise to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name| Type  | Mandatory| Description    |
+| ------ | ------ | ---- | -------- |
+| path   | string | Yes  | Path of the target file.|
+
+**Return value**
+
+| Type                 | Description        |
+| --------------------- | ------------ |
+| Promise<string> | Security label obtained.|
+
+**Example**
+
+  ```js
+  securityLabel.getSecurityLabel(path).then((type) => {
+      console.log("getSecurityLabel successfully, Label: " + type);
+  }).catch((err) => {
+      console.log("getSecurityLabel failed with error message: " + err.message + ", error code: " + err.code);
+  });
+  ```
+
+## securityLabel.getSecurityLabel
+
+getSecurityLabel(path:string, callback:AsyncCallback<string>): void
+
+Obtains the security label of a file in asynchronous mode. This API uses a callback to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name  | Type                       | Mandatory| Description                      |
+| -------- | --------------------------- | ---- | -------------------------- |
+| path     | string                      | Yes  | Path of the target file.                  |
+| callback | AsyncCallback<string> | Yes  | Callback invoked to return the security label obtained.|
+
+**Example**
+
+  ```js
+  securityLabel.getSecurityLabel(path, (err, type) => {
+    if (err) {
+      console.log("getSecurityLabel failed with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.log("getSecurityLabel successfully, Label: " + type);
+    }
+  });
+  ```
+## securityLabel.getSecurityLabelSync
+
+getSecurityLabelSync(path:string):string
+
+Obtains the security label of a file in synchronous mode.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name| Type  | Mandatory| Description    |
+| ------ | ------ | ---- | -------- |
+| path   | string | Yes  | Path of the target file.|
+
+**Return value**
+
+| Type  | Description        |
+| ------ | ------------ |
+| string | Security label obtained.|
+
+**Example**
+
+```js
+let type = securityLabel.getSecurityLabelSync(path);
+console.log("getSecurityLabel successfully, Label: " + type);
+```

en/application-dev/reference/apis/js-apis-file-statvfs.md

+# @ohos.file.statvfs (File System Space Statistics)
+
+The **statfs** module provides APIs for obtaining file system information, including the total number of bytes and the number of idle bytes of the file system.
+
+> **NOTE**
+>
+> - The initial APIs of this module are supported since API version 9. Newly added APIs will be marked with a superscript to indicate their earliest API version.
+> - The APIs of this module support processing of error codes. For details, see [File Management Error Codes](../errorcodes/errorcode-filemanagement.md).
+
+## Modules to Import
+
+```js
+import statvfs from '@ohos.file.statvfs';
+```
+## statvfs.getFreeSize
+
+getFreeSize(path:string):Promise<number>
+
+Obtains the number of free bytes of the specified file system in asynchronous mode. This API uses a promise to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name| Type  | Mandatory| Description                        |
+| ------ | ------ | ---- | ---------------------------- |
+| path   | string | Yes  | File path of the file system.|
+
+**Return value**
+
+| Type                 | Description          |
+| --------------------- | -------------- |
+| Promise<number> | Promise used to return the number of free bytes obtained.|
+
+**Example**
+
+  ```js
+  let path = "/dev";
+  statfs.getFreeSize(path).then((number) => {
+    console.info("getFreeSize promise successfully, Size: " + number);
+  }).catch((err) => {
+    console.info("getFreeSize failed with error message: " + err.message + ", error code: " + err.code);
+  });
+  ```
+
+## statfs.getFreeSize
+
+getFreeSize(path:string, callback:AsyncCallback<number>): void
+
+Obtains the number of free bytes of the specified file system in asynchronous mode. This API uses an asynchronous callback to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name  | Type                       | Mandatory| Description                        |
+| -------- | --------------------------- | ---- | ---------------------------- |
+| path     | string                      | Yes  | File path of the file system.|
+| callback | AsyncCallback<number> | Yes  | Callback invoked to return the number of free bytes obtained.|
+
+**Example**
+
+  ```js
+  let path = "/dev";
+  statfs.getFreeSize(path, (err, number) => {
+    if (err) {
+      console.info("getFreeSize failed with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.info("getFreeSize callback successfully, Size: " + number);
+    }
+  });
+  ```
+
+## statfs.getTotalSize
+
+getTotalSize(path: string): Promise<number>
+
+Obtains the total number of bytes of the specified file system in asynchronous mode. This API uses a promise to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name| Type  | Mandatory| Description                        |
+| ---- | ------ | ---- | ---------------------------- |
+| path | string | Yes  | File path of the file system.|
+
+**Return value**
+
+| Type                 | Description        |
+| --------------------- | ------------ |
+| Promise<number> | Promise used to return the total number of bytes obtained.|
+
+**Example**
+
+  ```js
+  let path = "/dev";
+  statfs.getTotalSize(path).then((number) => {
+    console.info("getTotalSize promise successfully, Size: " + number);
+  }).catch((err) => {
+    console.info("getTotalSize with error message: " + err.message + ", error code: " + err.code);
+  });
+  ```
+
+## statfs.getTotalSize
+
+getTotalSize(path: string, callback: AsyncCallback<number>): void
+
+Obtains the total number of bytes of the specified file system in asynchronous mode. This API uses an asynchronous callback to return the result.
+
+**System capability**: SystemCapability.FileManagement.File.FileIO
+
+**Parameters**
+
+| Name  | Type                       | Mandatory| Description                        |
+| -------- | --------------------------- | ---- | ---------------------------- |
+| path     | string                      | Yes  | File path of the file system.|
+| callback | AsyncCallback<number> | Yes  | Callback invoked to return the total number of bytes obtained.  |
+
+**Example**
+
+  ```js
+  let path = "/dev";
+  statfs.getTotalSize(path, (err, number) => {
+    if (err) {
+      console.info("getTotalSize with error message: " + err.message + ", error code: " + err.code);
+    } else {
+      console.info("getTotalSize promise successfully, Size: " + number);
+    }
+  });
+  ```

en/application-dev/reference/apis/js-apis-statfs.md

@@ -4,7 +4,9 @@ The **statfs** module provides APIs for obtaining file system information, inclu
 
 > **NOTE**
 >
-> The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version.
+> - The initial APIs of this module are supported since API version 8. Newly added APIs will be marked with a superscript to indicate their earliest API version.
+>
+> - The APIs provided by this module are deprecated since API version 9. You are advised to use [@ohos.file.statvfs](js-apis-file-statvfs.md).
 
 ## Modules to Import
 
@@ -21,15 +23,15 @@ Obtains the number of free bytes of the specified file system in asynchronous mo
 
 **Parameters**
 
-  | Name| Type  | Mandatory| Description                        |
-  | ------ | ------ | ---- | ---------------------------- |
-  | path   | string | Yes  | File path of the file system.|
+| Name| Type  | Mandatory| Description                        |
+| ------ | ------ | ---- | ---------------------------- |
+| path   | string | Yes  | File path of the file system.|
 
 **Return value**
 
-  | Type                 | Description          |
-  | --------------------- | -------------- |
-  | Promise<number> | Promise used to return the number of free bytes obtained.|
+| Type                 | Description          |
+| --------------------- | -------------- |
+| Promise<number> | Promise used to return the number of free bytes obtained.|
 
 **Example**
 
@@ -52,10 +54,10 @@ Obtains the number of free bytes of the specified file system in asynchronous mo
 
 **Parameters**
 
-  | Name  | Type                       | Mandatory| Description                        |
-  | -------- | --------------------------- | ---- | ---------------------------- |
-  | path     | string                      | Yes  | File path of the file system.|
-  | callback | AsyncCallback<number> | Yes  | Callback invoked to return the number of free bytes obtained.|
+| Name  | Type                       | Mandatory| Description                        |
+| -------- | --------------------------- | ---- | ---------------------------- |
+| path     | string                      | Yes  | File path of the file system.|
+| callback | AsyncCallback<number> | Yes  | Callback invoked to return the number of free bytes obtained.|
 
 **Example**
 
@@ -79,15 +81,15 @@ Obtains the total number of bytes of the specified file system in asynchronous m
 
 **Parameters**
 
-  | Name| Type  | Mandatory| Description                        |
-  | ---- | ------ | ---- | ---------------------------- |
-  | path | string | Yes  | File path of the file system.|
+| Name| Type  | Mandatory| Description                        |
+| ---- | ------ | ---- | ---------------------------- |
+| path | string | Yes  | File path of the file system.|
 
 **Return value**
 
-  | Type                 | Description        |
-  | --------------------- | ------------ |
-  | Promise<number> | Promise used to return the total number of bytes obtained.|
+| Type                 | Description        |
+| --------------------- | ------------ |
+| Promise<number> | Promise used to return the total number of bytes obtained.|
 
 **Example**
 
@@ -110,10 +112,10 @@ Obtains the total number of bytes of the specified file system in asynchronous m
 
 **Parameters**
 
-  | Name  | Type                       | Mandatory| Description                        |
-  | -------- | --------------------------- | ---- | ---------------------------- |
-  | path     | string                      | Yes  | File path of the file system.|
-  | callback | AsyncCallback<number> | Yes  | Callback invoked to return the total number of bytes obtained.  |
+| Name  | Type                       | Mandatory| Description                        |
+| -------- | --------------------------- | ---- | ---------------------------- |
+| path     | string                      | Yes  | File path of the file system.|
+| callback | AsyncCallback<number> | Yes  | Callback invoked to return the total number of bytes obtained.  |
 
 **Example**
 

en/application-dev/reference/errorcodes/errorcode-filemanagement.md

 # File Management Error Codes
-The error codes of the file management subsystem consist of the following:
-
-- Basic file I/O error codes
-- User data management error codes
-- User file access error codes
-- Spatial statistics error codes
+The error codes of the file management subsystem consist of the following:<br>- Basic file I/O error codes<br>- User data management error codes<br>- User file access error codes<br>- Spatial statistics error codes
 
 ## Basic File I/O Error Codes
 
@@ -719,3 +714,41 @@ Fail to notify agent
 
 **Solution**
 Check whether the client is normal.
+
+## Error Code Adaptation
+The APIs provided by the file management subsystem support exception handling.
+Sample code for exception handling in a synchronous API:
+```js
+import fs from '@ohos.file.fs'
+
+try {
+    let file = fs.openSync(path, fs.OpenMode.READ_ONLY);
+} catch (err) {
+    console.error("openSync errCode:" + err.code + ", errMessage:" + err.message);
+}
+```
+Sample code for exception handling in an asynchronous API (promise):
+```js
+import fs from '@ohos.file.fs'
+
+try {
+    let file = await fs.open(path, fs.OpenMode.READ_ONLY);
+} catch (err) {
+    console.error("open promise errCode:" + err.code + ", errMessage:" + err.message);
+}
+```
+
+Sample code for exception handling in an asynchronous API (callback):
+```js
+import fs from '@ohos.file.fs'
+
+try {
+    fs.open(path, fs.OpenMode.READ_ONLY, function(e, file){ // Asynchronous thread (such as the system call) errors are obtained via a callback.
+        if (e) {
+            console.error("open in async errCode:" + e.code + ", errMessage:" + e.message);
+        }
+    });
+} catch (err) {// Main thread errors (such as invalid parameters) are obtained by try catch.
+    console.error("open callback errCode:" + err.code + ", errMessage:" + err.message);
+}
+```