const hours = ["00", "01", "02", "03", "04", "05", "06", "07", "08", "09", "10", "11", "12", "13", "14", "15", "16", "17", "18", "19", "20", "21", "22", "23"];
document.querySelectorAll(".hours").forEach(select => {
const frag = document.createDocumentFragment();
frag.append(new Option("-",""))
hours.forEach(h => {
frag.append(new Option(h,h))
})
select.append(frag)
});
Fun times