<!DOCTYPE html>
<html lang="en-US">
<head>
<style>
div{
height:150px;
width:300px;
margin:25px;
padding:10px;
border:3px solid black;
}
</style>
</head>
<body>
<div>
<p><b>offsetWidth</b> = border-left + boder-right + padding-left + padding-right + width;</p>
<p><b>offsetWidth</b> = 3 + 3 + 10 + 10 + 300;</p>
<p><b>offsetWidth</b> = 326;</p>
</div>
<p>Click on the button to display the offsetWidth of the div.</p>
<button onclick="myFunction()">Click Me</button>
<p id="point"></p>
<script>
var x = document.getElementById("point");
var elem = document.getElementsByTagName("div")[0];
function myFunction(){
x.innerHTML = "offsetWidth = " + elem.offsetWidth;
}
</script> </body>
</html>