RxJS repeat depending on emitted value

Question

I am trying to repeat a promise call depending on the value returned in condition field. The following block doesn't work because v is undefined and randomly throws TypeError: Cannot read property 'condition' of undefined

the o/p of console.log is { Items: [ 1, 2, 3, 4, 5 ], condition: 5, time: 1513827310333 }

JSFiddle

const source = Rx.Observable.fromPromise(
  Promise.resolve({
    Items: [1, 2, 3, 4, 5],
    condition: Math.floor(Math.random() * 10),
    time: +new Date()
  })
);

source
  .map(val => val)
  .repeatWhen(val => {
    return val.map(v => { // v is undefined
      if (v.condition > 0) {
        return Rx.Observable.of(v);
      } else {
        return Rx.Observable.empty();
      }
    });
  })
  .finally(() => {
    done();
  })
  .subscribe(val => console.log(val));

Answer 1

Got it working with an external flag an the source is evaluated for every repetition.

 const source = Rx.Observable.defer(() => Promise.resolve({ Items: [1, 2, 3, 4, 5], condition: Math.floor(Math.random() * 10), time: +new Date() }) ); let condition = false; source .repeatWhen(notifications => { return notifications .scan(() => { return condition; }, false) .delay(100) .takeWhile(() => { return condition; }); }) .do(x => (condition = x.condition !== 0)) .finally(console.log("done")) .subscribe(console.log); 

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