1# Using Emitter for Inter-Thread Communication 2 3[Emitter](../../reference/apis-basic-services-kit/js-apis-emitter.md) provides APIs for sending and processing events between threads, including the APIs for processing events that are subscribed to in persistent or one-shot manner, unsubscribing from events, and emitting events to the event queue. 4 5To develop the Emitter mode, perform the following steps: 6 71. Subscribe to an event. 8 9 ```ts 10 import { emitter } from '@kit.BasicServicesKit'; 11 import { promptAction } from '@kit.ArkUI'; 12 import { hilog } from '@kit.PerformanceAnalysisKit'; 13 14 const TAG: string = 'ThreadModel'; 15 const DOMAIN_NUMBER: number = 0xFF00; 16 ``` 17 ```ts 18 // Define an event with eventId 1. 19 let event: emitter.InnerEvent = { 20 eventId: 1 21 }; 22 23 // Trigger the callback after the event with eventId 1 is received. 24 let callback = (eventData: emitter.EventData): void => { 25 promptAction.showToast({ 26 message: JSON.stringify(eventData) 27 }); 28 hilog.info(DOMAIN_NUMBER, TAG, 'event callback:' + JSON.stringify(eventData)); 29 }; 30 31 // Subscribe to the event with eventId 1. 32 emitter.on(event, callback); 33 promptAction.showToast({ 34 message: JSON.stringify('emitter subscribe success') 35 }); 36 ``` 37 382. Emit the event. 39 ```ts 40 // Define an event with eventId 1 and priority Low. 41 let event: emitter.InnerEvent = { 42 eventId: 1, 43 priority: emitter.EventPriority.LOW 44 }; 45 46 let eventData: emitter.EventData = { 47 data: { 48 content: 'c', 49 id: 1, 50 isEmpty: false 51 } 52 }; 53 54 // Emit the event with eventId 1 and event content eventData. 55 emitter.emit(event, eventData); 56 ``` 57