offsetParent is containing block
1. position: static; offsetTop 元素的上外边距到containing block的上内边距 (containing block的padding + element.margin)
<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<section>
<article></article>
</section>
<style>
* {
margin: 0;
padding: 0;
}
section {
width: 300px;
height: 3%;
margin: 10px;
border: 20px dotted peru;
padding: 30px;
background-color: tan;
position: relative;
}
article {
width: 100px;
height: 100px;
margin: 10px;
border: 20px dashed wheat;
padding: 30px;
background-color: aqua;
}
</style>
<script>
const section = document.querySelector('section')
const article = document.querySelector('article')
</script>
</body>
</html>
2. position: absolute; 先理解top(margin-top到containing block的内边距), 因此, offsetTop top + margin-top
<!DOCTYPE html>
<html lang="en-US">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<section>
<article></article>
</section>
<style>
* {
margin: 0;
padding: 0;
}
section {
width: 300px;
height: 3%;
margin: 10px;
border: 20px dotted peru;
padding: 30px;
background-color: tan;
position: relative;
}
article {
width: 100px;
height: 100px;
margin: 10px;
border: 20px dashed wheat;
padding: 30px;
background-color: aqua;
position: absolute;
top: 20px;
}
</style>
<script>
const section = document.querySelector('section')
const article = document.querySelector('article')
</script>
</body>
</html>
标签：offsetParent,section,padding,offsetLeft,position,article,20px,margin,CSS From： https://www.cnblogs.com/dissipate/p/17470844.html