rxjs throwing an error once http request returns a specific value

Question

I did write an Observable which is polling an URL which completes once a specific value is returned.

private checkPairingStatus(paringModel: any): Observable<ResponseObject> {
    let data = { id: 1234 };
    return Observable
        .interval(2000)
        .switchMap(() => this.get<ResponseObject>('http://api/getstatus', data))
        .first(r => r.Status === 'success') // once our pairing is active we emit that
        .timeout(90000, Observable.throw(new Error('Timeout ocurred')));
        // todo: find a way to abort the interval once the PairingStatus hits the 'canceled' status.
}

This works pretty fine but I'm struggling on how to throw an exception once my respone for example hits the following status "r.Status === 'canceled'".

Thanks for any hint on that!

Regards Lukas

Answer 1

You can just use do() and throw an Error with whatever condition you need:

return Observable
    .interval(200)
    .do(val => {
        if (val == 5) {
            throw new Error('everything is broken');
        }
    })
    .subscribe(
        val => console.log(val),
        err => console.log('Error:', err.message)
    );

This prints to console:

0
1
2
3
4
Error: everything is broken

In your case you'll want to test a condition such as r.Status === 'canceled' or whatever.