Demo:  bufferCount

bufferCount operator keeps collecting the incoming data into a new array and emits as the item count reaches the specified max count.

bufferCount(maxItemCount)

let input = timer(0,1500).pipe(take(7));

//buffer and emit every 3 items
let process = bufferCount(3);

let output=input.pipe(process).subscribe(v=>console.log(v))