Creating an observable that emits values periodically (error: observer.timer is not a function)

Question

I have an object that looks like this: [{ timestamp: object }]
The timestamp is created timestamp = Date.now();

Now, I am looking for a way to create an Observable that emits the objects in the real sequence, i.e. when the time between entries is 200ms then it needs to wait 200ms, if it's 2.5 seconds then it needs to wait 2500ms.

I get the difference by subtracting the two adjacent index values from each other.

My code is here:

startReplay() {
  this.recordingRunning = true;
  const replayValues = this.recordedListeningValues;
  this.formObservable = Observable.create(function(observer) {
    let lastTs;
    Object.keys(replayValues).forEach(function(key) {
        observer.timer(Math.floor((Number(key) - lastTs) / 1000)).next(key, lastTs);
        lastTs = Number(key);
    });
  });
  var source = this.formObservable.subscribe(x => console.log(x));
}

It throws the error: observer.timer is not a function

At the moment, I am only trying to log the differences between the timestamps in seconds. Now, I want to emit it in the differences between the two timestamps.

Observable.interval - I guess this is used to create an observable emit periodically. — Anurag Singh Bisht
– Anurag Singh Bisht, Commented Aug 17, 2017 at 15:47
Yeah, I think I wouldn't be able to do this using timer, would I? — Spurious
– Spurious, Commented Aug 17, 2017 at 15:52

Brandon · Accepted Answer · 2017-08-17 19:48:37Z

1

You can use delayWhen operator. But you need to know the timestamp of the start of the recording so that you can calculate the time of each event relative to the start of the recording

const startOfRecording = ??? // Date.now() when recording started
const recordedValues = ???

// each time someone subscribes to this observable
// the recorded events will play back in "real time"
this.formObservable = Observable
    .from(Object.keys(replayValues))
    .delayWhen(key => Observable.timer(key - startOfRecording))
    .map(key => replayValues[key]);

answered Aug 17, 2017 at 19:48

Brandon

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3 Comments

Spurious Over a year ago

Thanks, I will give it a try tomorrow and report back. This looks promising.

Spurious Over a year ago

Thank you, that works! How can I determine what the Observable does onComplete? I knew how to do it on Observer.

Brandon Over a year ago

Add a .finally(() => console.log("done")) to the end

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