Demo:  startWith

startWith adds the given set of values to the start of the incoming data stream.

startWith(x,y,z)

//3 items every 1.5 sec, starting at 1 sec
let input_1 = timer(1000, 1500).pipe(take(3)) ;

//startWith adds 10 to the start of the incoming stream.
let process = startWith(10);

let output = input_1.pipe(process).subscribe(v=>console.log(v))