<!DOCTYPE html>
<html lang="en-US">
<body>
<ol><li>Apple</li></ol>
<button onclick="myFunction()">Add Mango</button>
<script>
var parentNode = document.getElementsByTagName("ol")[0];
function insertAfter(newNode, refNode){
refNode.parentNode.insertBefore(newNode, refNode.nextSibling);
}
function myFunction(){
var newNode = document.createElement("li");
var textnode = document.createTextNode("Mango");
newNode.appendChild(textnode);
insertAfter(newNode, parentNode.childNodes[0]);
}
</script> </body>
</html>