How to emit every n-th value?

Question

I'm using mousemove event to create an observable.

Observable.fromEvent(document, 'mousemove')

I need to emit every 10-th event. What do I do?

Answer 1

I can think of four different ways to do it:

bufferCount()

Observable.range(1, 55)
  .bufferCount(10)
  .map(arr => arr[arr.length - 1])
  .subscribe(val => console.log(val));

windowCount()

Observable.range(1, 55)
  .windowCount(10)
  .switchMap(window => window.takeLast(1))
  .subscribe(val => console.log(val));

debounce()

let source = Observable.range(1, 55).publish();

source
  .debounce(val => debounceNotifier)
  .subscribe(val => console.log(val));

let debounceNotifier = source
  .bufferCount(10)
  .publish();
debounceNotifier.connect();

source.connect();

scan()

Observable.range(1, 55)
  .scan((acc, val) => {
    if (acc.length === 10) {
      acc = [];
    }
    acc.push(val);
    return acc;
  }, [])
  .filter(acc => acc.length === 10)
  .map(acc => acc[acc.length - 1])
  .subscribe(val => console.log(val));

However, when using scan() it'll will discard the last value 55.

See demo for all of them: https://jsbin.com/yagayot/14/edit?js,console