append position
<!-- (A) HTML LIST -->
<ol id="demoB">
<li>First</li>
<li>Second</li>
</ol>
<!-- (B) JAVASCRIPT ADD -->
<script>
function addItemPos (top) {
// (B1) CREATE NEW LIST ITEM
var item = document.createElement("li");
item.innerHTML = "New";
// (B2) APPEND ITEM TO TOP
if (top) {
document.getElementById("demoB").insertAdjacentElement('afterbegin', item);
}
// (B3) IN THE MIDDLE
else {
var allItems = document.querySelectorAll("#demoB li");
var allLength = allItems.length;
var middle = Math.ceil(allLength/2) - 1;
if (middle<0) { middle = 0; }
allItems[middle].insertAdjacentElement('afterend', item);
}
}
</script>
<input type="button" value="Add Top" onclick="addItemPos(1)"/>
<input type="button" value="Add Middle" onclick="addItemPos()"/>