const numbersEl = document.getElementById('numbers');
const lettersEl = document.getElementById('letters');
const resultEl = document.getElementById('result');
// An array
var numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
var letters = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K"]

// Let's create streams for our 
var numbers$ = Rx.Observable
    .interval(750)
    .take(12)
    .map(i => numbers[i])

var letters$ = Rx.Observable
    .interval(1000)
    .take(11)
    .map(i => letters[i])

var result$ = Rx.Observable.zip(numbers$, letters$)

numbers$.subscribe(n => numbersEl.innerHTML = n);
letters$.subscribe(n => lettersEl.innerHTML = n);
result$.subscribe(n => resultEl.innerHTML = n);