<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
<style>
div {
width: 100px;
height: 100px;
padding: 10px;
border: 10px solid #000;
margin: 100px;
background-color: pink;
}
</style>
</head>
<body>
<div class="box"></div>
<script>
var div = document.getElementsByTagName("div")[0];
//offsetHeight和offsetWidth: 可以检测盒子的宽高。
//包括宽高本身，padding，border。不包括margin
//offsetHeight = height+padding+border;(不加margin)
//offsetWidth = width+padding+border;(不加margin)
console.log(div.offsetHeight);
console.log(typeof div.offsetHeight); //number
</script>
</body>
</html>
原文：http://www.cnblogs.com/sj1988/p/6594085.html