From f883ce1cc3f32e9dfcacba6c79b21cf3f1831d69 Mon Sep 17 00:00:00 2001
From: "ester.zhou" <ester.zhou@huawei.com>
Date: Wed, 16 Feb 2022 18:13:44 +0800
Subject: [PATCH] add doc

Signed-off-by: ester.zhou <ester.zhou@huawei.com>
---
 .../reference/apis/js-apis-emitter.md         | 144 ++++++++++++++++++
 1 file changed, 144 insertions(+)
 create mode 100644 en/application-dev/reference/apis/js-apis-emitter.md

diff --git a/en/application-dev/reference/apis/js-apis-emitter.md b/en/application-dev/reference/apis/js-apis-emitter.md
new file mode 100644
index 0000000000..7b96f6e40c
--- /dev/null
+++ b/en/application-dev/reference/apis/js-apis-emitter.md
@@ -0,0 +1,144 @@
+# Emitter
+
+> Note: The initial APIs of this module are supported since API version 7.
+
+## Modules to Import
+
+```javascript
+import emitter from '@ohos.events.emitter'
+```
+
+## System Capabilities
+
+```javascript
+SystemCapability.Notification.Emitter
+```
+
+## Required Permissions
+
+None
+
+## EventPriority
+
+Enumerates the event emit priority levels.
+
+| 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.|
+
+## 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.
+
+**Parameters**
+
+| 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.|
+
+**Example**
+
+```javascript
+var innerEvent = {
+    eventId : 1
+};
+var callback = (eventData) => {
+    console.info('callback');
+};
+emitter.on(innerEvent, callback);
+```
+
+## emitter.once
+
+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.
+
+**Parameters**
+
+| 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.|
+
+**Example**
+
+```javascript
+var innerEvent = {
+    eventId : 1
+};
+var callback = (eventData) => {
+    console.info('once callback');
+};
+emitter.once(innerEvent, callback);
+```
+
+## emitter.off
+
+off(eventId: number): void
+
+Unsubscribes from an event.
+
+**Parameters**
+
+| Name| Type| Mandatory| Description|
+| ------- | ------ | ---- | -------------- |
+| eventId | number | Yes| Event ID.|
+
+**Example**
+
+```javascript
+emitter.off(1);
+```
+
+## emitter.emit
+
+emit(event: InnerEvent, data?: EventData): void
+
+Emits an event to the event queue.
+
+**Parameters**
+
+| Name| Type| Mandatory| Description|
+| ------ | ------------------------- | ---- | -------------- |
+| event  | [InnerEvent](#InnerEvent) | Yes| Event to emit.|
+| data   | [EventData](#EventData)   | No| Data carried by the event.|
+
+**Example**
+
+```javascript
+var eventData = {
+    data: {
+        1:"t",
+        'content':"c",
+        "id":1,
+    }};
+var innerEvent = {
+    eventId : 1,
+    priority: emitter.EventPriority.HIGH
+};
+emitter.emit(innerEvent, eventData);
+```
+
+## InnerEvent
+
+Describes an intra-process event.
+
+| 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.|
+
+## EventData
+
+Describes the data passed in the event.
+
+| Name| Type| Readable| Writable| Description|
+| ---- | ------------------ | ---- | ---- | -------------- |
+| data | [key: string]: any | Yes| Yes| Data carried by the event.|
-- 
GitLab