how to use the throwerror function from the rxjs library in typescript

To use the throwError function from the RxJS library in TypeScript, you first need to import it from the library:

index.ts
import { throwError } from 'rxjs';
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The throwError function is used to create an observable that immediately emits an error notification. You can pass an error object or a string message as an argument to the throwError function. For example:

index.ts
throwError('Something went wrong');
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or

index.ts
throwError(new Error('Unexpected error occurred'));
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You can also use the catchError operator to handle the error notification emitted by the throwError function. For example:

index.ts
import { throwError, catchError } from 'rxjs';
import { of } from 'rxjs';

throwError('Something went wrong')
.pipe(
  catchError(error => {
    console.error(error);
    return of('Default value');
  })
)
.subscribe(value => console.log(value));
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In this example, if an error is emitted by the throwError function, it will be caught by the catchError operator and a default value will be returned instead. The subscribe method will then log the default value to the console.