update doc

Signed-off-by: Nesterzhou <ester.zhou@huawei.com>

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

@@ -8,12 +8,6 @@
 import emitter from '@ohos.events.emitter'
 ```
 
-## System Capabilities
-
-```javascript
-SystemCapability.Notification.Emitter
-```
-
 ## Required Permissions
 
 None
@@ -22,25 +16,27 @@ None
 
 Enumerates the event emit priority levels.
 
-| Name| Value| Description|
+| Name     | Value  | Description                                             |
 | --------- | ---- | ------------------------------------------------- |
-| IMMEDIATE | 0    | The event will be emitted immediately.|
-| HIGH      | 1    | The event will be emitted before low-priority events.|
-| LOW       | 2    | The event will be emitted before idle-priority events. By default, an event is in LOW priority.|
-| IDLE      | 3    | The event will be emitted after all the other events.|
+| IMMEDIATE | 0    | The event will be emitted immediately.<br>**System capability**: SystemCapability.Notification.Emitter                               |
+| HIGH      | 1    | The event will be emitted before low-priority events.<br>**System capability**: SystemCapability.Notification.Emitter                        |
+| LOW       | 2    | The event will be emitted before idle-priority events. By default, an event is in LOW priority.<br>**System capability**: SystemCapability.Notification.Emitter|
+| IDLE      | 3    | The event will be emitted after all the other events.<br>**System capability**: SystemCapability.Notification.Emitter         |
 
 ## emitter.on
 
 on(event: [InnerEvent](#innerevent), callback: Callback\<[EventData](#eventdata)\>): void
 
-Subscribes to an event in persistent manner. This method uses a callback to return the event.
+Subscribes to an event in persistent manner. This API uses a callback to return the event.
+
+**System capability**: SystemCapability.Notification.Emitter
 
 **Parameters**
 
-| Name| Type| Mandatory| Description|
+| Name  | Type                               | Mandatory| Description                    |
 | -------- | ----------------------------------- | ---- | ------------------------ |
-| event    | [InnerEvent](#innerevent) | Yes| Event to subscribe to in persistent manner.|
-| callback | Callback\<[EventData](#eventdata)\> | Yes| Callback used to return the event.|
+| event    | [InnerEvent](#innerevent)           | Yes  | Event to subscribe to in persistent manner.          |
+| callback | Callback\<[EventData](#eventdata)\> | Yes  | Callback used to return the event.|
 
 **Example**
 
@@ -56,16 +52,18 @@ emitter.on(innerEvent, callback);
 
 ## emitter.once
 
-once(event: [InnerEvent](#innerevent), callback: Callback\<[EventData](#eventdata)\>): **void**
+once(event: [InnerEvent](#innerevent), callback: Callback\<[EventData](#eventdata)\>): void
 
 Subscribes to an event in one-shot manner and unsubscribes from it after the event callback is received.
 
+**System capability**: SystemCapability.Notification.Emitter
+
 **Parameters**
 
-| Name| Type| Mandatory| Description|
+| Name  | Type                               | Mandatory| Description                    |
 | -------- | ----------------------------------- | ---- | ------------------------ |
-| event    | [InnerEvent](#innerevent) | Yes| Event to subscribe to in one-shot manner.|
-| callback | Callback\<[EventData](#eventdata)\> | Yes| Callback used to return the event.|
+| event    | [InnerEvent](#innerevent)           | Yes  | Event to subscribe to in one-shot manner.          |
+| callback | Callback\<[EventData](#eventdata)\> | Yes  | Callback used to return the event.|
 
 **Example**
 
@@ -85,11 +83,13 @@ off(eventId: number): void
 
 Unsubscribes from an event.
 
+**System capability**: SystemCapability.Notification.Emitter
+
 **Parameters**
 
-| Name| Type| Mandatory| Description|
-| ------- | ------ | ---- | -------------- |
-| eventId | number | Yes| Event ID.|
+| Name | Type  | Mandatory| Description  |
+| ------- | ------ | ---- | ------ |
+| eventId | number | Yes  | Event ID.|
 
 **Example**
 
@@ -103,19 +103,21 @@ emit(event: InnerEvent, data?: EventData): void
 
 Emits an event to the event queue.
 
+**System capability**: SystemCapability.Notification.Emitter
+
 **Parameters**
 
-| Name| Type| Mandatory| Description|
+| Name| Type                     | Mandatory| Description          |
 | ------ | ------------------------- | ---- | -------------- |
-| event  | [InnerEvent](#innerevent) | Yes| Event to emit.|
-| data   | [EventData](#eventdata) | No| Data carried by the event.|
+| event  | [InnerEvent](#innerevent) | Yes  | Event to emit.    |
+| data   | [EventData](#eventdata)   | No  | Data carried by the event.|
 
 **Example**
 
 ```javascript
 var eventData = {
     data: {
-        'content': "c",
+        "content": "c",
         "id": 1,
     }};
 var innerEvent = {
@@ -129,15 +131,15 @@ emitter.emit(innerEvent, eventData);
 
 Describes an intra-process event.
 
-| Name| Type| Readable| Writable| Description|
+| Name    | Type                       | Readable| Writable| Description                              |
 | -------- | ------------------------------- | ---- | ---- | ---------------------------------- |
-| eventId  | number                          | Yes| Yes| Event ID, which is used to identify an event.|
-| priority | [EventPriority](#eventpriority) | Yes| Yes| Emit priority of the event.|
+| eventId  | number                          | Yes  | Yes  | Event ID, which is used to identify an event.<br>**System capability**: SystemCapability.Notification.Emitter|
+| priority | [EventPriority](#eventpriority) | Yes  | Yes  | Emit priority of the event.<br>**System capability**: SystemCapability.Notification.Emitter                |
 
 ## EventData
 
 Describes the data passed in the event.
 
-| Name| Type| Readable| Writable| Description|
+| Name| Type          | Readable| Writable| Description          |
 | ---- | ------------------ | ---- | ---- | -------------- |
-| data | [key: string]: any | Yes| Yes| Data carried by the event.|
+| data | [key: string]: any | Yes  | Yes  | Data carried by the event. The data type can be String, Integer, or Boolean.<br>**System capability**: SystemCapability.Notification.Emitter|