var d1 = document.getElementById('one');
d1.insertAdjacentHTML('afterend', '<div id="two">two</div>');
function insertAfter(newNode, existingNode) {
existingNode.parentNode.insertBefore(newNode, existingNode.nextSibling);
}
function insertAfter(newNode, existingNode) {
existingNode.parentNode.insertBefore(newNode, existingNode.nextSibling);
}<!DOCTYPE html>
<html>
<body>
<p id='up'>Up</p>
<p id="down">Down</p>
<button id="switchBtn" onclick="switch_place()">Switch place</button>
<script>
function switch_place(){
var downElement = document.getElementById("down")
var upElement = document.getElementById("up")
downElement.after(upElement);
document.getElementById('switchBtn').innerHTML = "Switched!"
}
</script>
</body>
</html>