//insert element
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>insert element</title>
<style>
body {
background-color: aquamarine;
}
#box {
height: 300px;
width: 100px;
color: black;
border: 1px solid black;
background-color: yellow;
}
</style>
</head>
<body>
<div id="box"> This is a div
<ul>
List
<li>item 1</li>
<li>item 2</li>
<li>item 3</li>
</ul>
</div>
<p class="para"> This is a paragraph</p>
<script>
let newbtn = document.createElement("button");
newbtn.innerText = "click";
let div = document.querySelector("div");
div.append(newbtn);//adds the end of the node(inside)
div.prepend(newbtn);//adds the start of the node(inside)
div.before(newbtn);//adds before the node(outside)
div.after(newbtn);//adds aftee the node(outside)
</script>
</body>
</html>