1# ErrorObserver 2 3The **ErrorObserver** module defines an observer to listen for application errors. It can be used as an input parameter in [errorManager.on](js-apis-app-ability-errorManager.md#errormanageron) to listen for errors that occur in the current application. 4 5## onUnhandledException 6 7onUnhandledException(errMsg: string): void; 8 9Called when an unhandled exception occurs in the JS runtime. 10 11**System capability**: SystemCapability.Ability.AbilityRuntime.Core 12 13**Parameters** 14 15| Name| Type| Mandatory| Description| 16| -------- | -------- | -------- | -------- | 17| errMsg | string | No| Message and error stack trace about the exception.| 18 19**Example** 20 21```ts 22import errorManager from '@ohos.app.ability.errorManager'; 23 24let observer = { 25 onUnhandledException(errorMsg) { 26 console.log('onUnhandledException, errorMsg: ' + JSON.stringify(errorMsg)); 27 } 28}; 29errorManager.on('error',observer); 30``` 31