<!DOCTYPE html>
<html>
<head>
<style>
#test {
top: 100px;
margin: 10px;
padding: 10px;
width: 300px;
position: relative;
border: 5px solid black
}
</style>
</head>
<body>
<div id="test">
<p>Click the button to get offsetTop for the test div.</p>
<p><button onclick="myFunction()">Try it</button></p>
<p>offsetTop is: <span id="demo"></span></p>
</div>
<script>
function myFunction() {
var testDiv = document.getElementById("test");
document.getElementById("demo").innerHTML = testDiv.offsetTop;
}
</script>
</body>
</html>