1# LoopObserver 2 3The **LoopObserver** module defines an observer to listen for event processing timeout. It can be used as an input parameter in [ErrorManager.on](./js-apis-app-ability-errorManager.md#errormanageron) to listen for the event processing time of the current application's main thread. 4 5> **NOTE** 6> 7> The initial APIs of this module are supported since API version 12. Newly added APIs will be marked with a superscript to indicate their earliest API version. 8 9## Modules to Import 10 11```ts 12import errorManager from '@ohos.app.ability.errorManager'; 13``` 14 15## LoopObserver.onLoopTimeOut 16 17onLoopTimeOut?(timeout: number): void 18 19Called when a timeout occurs for the main thread to process an event in the JS runtime. 20 21**System capability**: SystemCapability.Ability.AbilityRuntime.Core 22 23**Parameters** 24 25| Name| Type| Mandatory| Description| 26| -------- | -------- | -------- | -------- | 27| timeout | number | Yes| Actual execution time of the main thread.| 28 29**Example** 30 31```ts 32import errorManager from '@ohos.app.ability.errorManager'; 33 34let observer: errorManager.LoopObserver = { 35 onLoopTimeOut(timeout: number) { 36 console.log('Duration timeout: ' + timeout); 37 } 38}; 39errorManager.on("loopObserver", 1, observer); 40``` 41