Select Option

<select id="genres">
<option value="rock">Rock</option>
<option value="blues" selected>Blues</option>
</select>
<button onclick="myFunction()">
click me
</button>
<script>
function myFunction() {
// 1)
var selectedOption = genres.options[genres.selectedIndex];
alert( selectedOption.value );

// 2) aggiunge un altro Item
var newOption = new Option("Mio", "Mio");
genres.append(newOption);

// 3)
newOption.selected = true;
}
</script>