前置知识：盒子模型
-
box-sizing: border-box
实际宽度 = width = content + padding + border
代码：此时为border-box
#container{
width: 300px;
height: 200px;
padding: 20px;
margin: 30px;
border:5px solid #ccc;
box-sizing: border-box;
overflow: auto;
background-color: #fff;
}
内容宽度为250x150
-
box-sizing: content-box
实际宽度 = width + padding + border
代码：此时为content-box
#container {
width: 300px;
height: 200px;
padding: 20px;
margin: 30px;
border: 5px solid #ccc;
/* box-sizing: border-box; */
overflow: auto;
background-color: #fff;
}
内容宽度为witdh 300x200
计算规则
- offsetHeight offsetWidth : border + padding + content
- clientHeight clientWidth: padding + content
- scrollHeight scrollWidth: padding + 实际内容尺寸
border-box 下情况
content-box 下情况
测试一下特别的scrollHeight 和 scrollWidth
改变代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
* {
padding: 0;
margin: 0;
}
body {
background-color: #f1f1f1;
}
#container {
width: 300px;
height: 200px;
padding: 20px;
margin: 30px;
border: 5px solid #ccc;
box-sizing: border-box;
overflow: auto;
background-color: #fff;
}
#content {
width: 600px;
height: 500px;
background-color: #f1f1f1;
display: inline-block;
}
</style>
</head>
<body>
<div id="container">
<div id="content">
<p> offsetHeight scrollHeight clientHeight区别</p>
</div>
</div>
<script>
const container = document.getElementById('container')
console.log('offsetHeight: ', container.offsetHeight)
console.log('offsetWidth: ', container.offsetWidth)
console.log('clientHeight: ', container.clientHeight)
console.log('clientWidth: ', container.clientWidth)
console.log('scrollHeight: ', container.scrollHeight)
console.log('scrollWidth: ', container.scrollWidth)
</script>
</body>
</html>
container的子元素比自身要大，内部变成可拖动区域，子元素大小为600x500
此时：
scrollHeight = 500px + padding(20px)*2 = 540px
scrollWidth = 600px + padding(20px)*2 = 640px
补充 scrollTop 和 scrollLeft
分别指可拖动区域被隐藏部分距离顶部和左边的距离。
