Demo:  from

The from operator creates an observable data stream out of an array of data.

//Hint: On the timescale above the output will look overlapped
let input = from([5, 15, 25, 40, 20]);

//let's add 1sec delay after each data to remove the overlap
let process = concatMap(v => of(v).pipe(delay(1000)));

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