<select id="xotfOBCH" >
<option value="1" >1</option>
<option value="2" selected="selected">2</option>
<option value="3">3</option>
</select>
<button id="inc">+</button>
<div id="res"></div>
<script>
inc.onclick = function() {
xotfOBCH.value = (+xotfOBCH.value + 1).toString();
xotfOBCH.dispatchEvent(new Event("change"));
}
xotfOBCH.onchange = function() {
res.innerText = this.value;
}
</script>