update doc

Signed-off-by: Nshawn_he <shawn.he@huawei.com>

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

@@ -158,7 +158,6 @@ Requests the temporary permission for the application to access the USB device.
   });
   ```
 
-
 ## usb.claimInterface
 
 claimInterface(pipe: USBDevicePipe, iface: USBInterface, force?: boolean): number
@@ -243,14 +242,13 @@ Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB devi
   console.log(`setConfiguration = ${ret}`);
   ```
 
-
 ## usb.setInterface
 
 setInterface(pipe: USBDevicePipe, iface: USBInterface): number
 
 Sets a USB interface.
 
-Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB device list and interfaces, call [usb.requestRight](#usbrequestright) to request the device access permission, and call [usb.connectDevice](#usbconnectdevice) to obtain **devicepipe** as an input parameter.
+Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB device list and interfaces, call [usb.requestRight](#usbrequestright) to request the device access permission, call [usb.connectDevice](#usbconnectdevice) to obtain **devicepipe** as an input parameter, and call [usb.claimInterface](#usbclaiminterface) to claim a USB interface..
 
 **System capability**: SystemCapability.USB.USBManager
 
@@ -290,7 +288,7 @@ Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB devi
 - **Return value**
   | Type| Description|
   | -------- | -------- |
-  | Uint8Array | Raw descriptor data. |
+  | Uint8Array | Raw descriptor data. The value **undefined** indicates that the operation has failed. |
 
 - **Example**
   ```js
@@ -316,7 +314,7 @@ Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB devi
 - **Return value**
   | Type| Description|
   | -------- | -------- |
-  | number | File descriptor of the USB device. |
+  | number | File descriptor of the USB device. The value **-1** indicates that the operation has failed. |
 
 - **Example**
   ```js
@@ -360,7 +358,7 @@ bulkTransfer(pipe: USBDevicePipe, endpoint: USBEndpoint, buffer: Uint8Array, tim
 
 Performs bulk transfer.
 
-Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB device list and endpoints, call [usb.requestRight](#usbrequestright) to request the device access permission, call [usb.connectDevice](#usbconnectdevice) to obtain **devicepipe** as an input parameter, and call [usb.claimInterface](#usbclaiminterface) to claim the USB interface.
+Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB device list and endpoints, call [usb.requestRight](#usbrequestright) to request the device access permission, call [usb.connectDevice](#usbconnectdevice) to obtain **devicepipe** as an input parameter, and call [usb.claimInterface](#usbclaiminterface) to claim a USB interface.
 
 **System capability**: SystemCapability.USB.USBManager
 
@@ -381,7 +379,7 @@ Before you do this, call [usb.getDevices](#usbgetdevices) to obtain the USB devi
   ```js
   // Call usb.getDevices to obtain a data set. Then, obtain a USB device and its access permission.
   // Pass the obtained USB device as a parameter to usb.connectDevice. Then, call usb.connectDevice to connect the USB device.
-  // Call usb.claimInterface to claim the USB interface. After that, call usb.bulkTransfer to start bulk transfer.
+  // Call usb.claimInterface to claim a USB interface. After that, call usb.bulkTransfer to start bulk transfer.
   usb.bulkTransfer(devicepipe, endpoint, buffer).then((ret) => {
    console.log(`bulkTransfer = ${JSON.stringify(ret)}`);
   });