how to use the catcherror function from the rxjs library in javascript

The catchError function is used in RxJS to handle errors that may occur in an Observable stream. The function takes a callback parameter which should return a new Observable or throw an error.

Here's an example of how to use catchError:

index.tsx
import { of } from 'rxjs';
import { catchError } from 'rxjs/operators';

const observable$ = of(1, 2, 3, 'test', 4, 5);

observable$.pipe(
  map(val => val.toUpperCase()), // this will throw an error on 'test'
  catchError(err => {
    console.error('Error caught:', err);
    return of('error handled');
  })
).subscribe(
  val => console.log('Next:', val),
  err => console.error('Error:', err),
  () => console.log('Complete')
);
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In this example, we are creating an Observable observable$ that emits an error when it encounters the string 'test' during the map operator.

We use the catchError operator to handle this error and log it to the console, before returning a new Observable that emits the string 'error handled'.

The next operator in the pipe receives the value emitted by catchError instead of the original value of 'test'.

The output of running this code will be:

index.tsx
Next: 1
Next: 2
Next: 3
Error caught: TypeError: val.toUpperCase is not a function
Next: error handled
Complete
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As you can see, the error was caught and the Observable continued emitting values after the error was handled.