Javascript rxjs handle every nth error

Question

In my code below I get a face from the camera every second. If I recognize the user, I get a token. If I don't recognize the user, I print an error.

The problem is that I don't want to spam the user with errors every second. How can I print the error on the nth consecutive failure?

subscription = getFaces()
.throttleTime(1000)
.switchMap(face => {
  return Observable.fromPromise(authenticateUserFace(face))
    .catch(err => {
      console.log('Not found')  // I want this to happen after 3 consecutive attempts
                                // But I don't want to retry
                                // I want a new value from the outer observable
      return Observable.empty()
    })
})
.subscribe((token) => {
  console.log('Found')
  console.log(token)
})

Mario Cianciolo · Accepted Answer · 2018-02-21 17:20:18Z

1

Just use a counter variable, and log to console only when it's a multiple of three:

const k = 3; // change this according to your needs
var counter = 0;

subscription = getFaces()
    .throttleTime(1000)
    .switchMap(face => {
        return Observable.fromPromise(authenticateUserFace(face))
            .catch(err => {
                counter++; // increment counter
                if (counter % k == 0) // this is true once every k times
                    console.log('Not found');

                return Observable.empty();
            })
    })
    .subscribe((token) => {
        console.log('Found');
        console.log(token);
    })

answered Feb 21, 2018 at 17:20

Mario Cianciolo

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