You’ll need to loop through your array elements, create a new DOM node for each and append it to your object:
var select = document.getElementById("selectNumber");
var options = ["1", "2", "3", "4", "5"];
for(var i = 0; i < options.length; i++) {
var opt = options[i];
var el = document.createElement("option");
el.textContent = opt;
el.value = opt;
select.appendChild(el);
}<select id="selectNumber">
<option>Choose a number</option>
</select>