方案划分为：
定位3种display:flex;JavaScriptdisplay:table-cell
方案一
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>方案一
</title>
<style>
*{
margin: 0;
padding:0;
}
html,
body{
height:100%;
overflow: hidden;
}
.box{
box-sizing: border-box;
width: 100px;
height: 50px;
line-height: 50px;
text-align: center;
font-size: 16px;
background-color: pink;
}
body{
position: relative;
}
.box{
position: absolute;
top: 50%;
left: 50%;
margin-top: -50px;
margin-left: -75px;
}
</style>
</head>
<body>
<div class="box">
方案一
</div>
</body>
</html>
这种方案要知道盒子(.box)的具体宽高，因为是通过宽和高来算margin的值的。
方案二
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>方案二
</title>
<style>
*{
margin: 0;
padding:0;
}
html,
body{
height:100%;
overflow: hidden;
}
.box{
box-sizing: border-box;
width: 100px;
height: 50px;
line-height: 50px;
text-align: center;
font-size: 16px;
background-color: pink;
}
body{
position: relative;
}
.box{
position: absolute;
top: 0;
left: 0;
right: 0;
bottom:0;
margin: auto;
}
</style>
</head>
<body>
<div class="box">
方案二
</div>
</body>
</html>
这种方案不用考虑盒子(.box)宽高，但是盒子(.box)一定要具备宽高。
方案三
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>方案三
</title>
<style>
*{
margin: 0;
padding:0;
}
html,
body{
height:100%;
overflow: hidden;
}
.box{
box-sizing: border-box;
width: 100px;
text-align: center;
font-size: 16px;
background-color: pink;
}
body{
position: relative;
}
.box{
position: absolute;
top: 50%;
left: 50%;
transform: translate(-50%,-50%);
}
</style>
</head>
<body>
<div class="box">
方案三
</div>
</body>
</html>
这种方式可以内容能撑开多高就多高，也可以按真实高度处理，这种方式不用具体宽高。但是存在兼容性问题。
方案四
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>方案四
</title>
<style>
*{
margin: 0;
padding:0;
}
html,
body{
height:100%;
overflow: hidden;
}
.box{
box-sizing: border-box;
width: 100px;
height: 50px;
line-height: 50px;
text-align: center;
font-size: 16px;
background-color: pink;
}
body{
display: flex;
justify-content: center;
align-items: center;
}
</style>
</head>
<body>
<div class="box">
方案四
</div>
</body>
</html>
在移动端经常会使用这种方式。
方案五
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>方案五
</title>
<style>
*{
margin: 0;
padding:0;
}
html,
body{
position: relative;
height:100%;
overflow: hidden;
}
body{
}
.box{
position: absolute;
box-sizing: border-box;
width: 100px;
height: 50px;
line-height: 50px;
text-align: center;
font-size: 16px;
background-color: pink;
}
</style>
</head>
<body>
<div class="box" id="box">
方案五
</div>
<script>
let html = document.documentElement,
winW = html.clientWidth,
winH = html.clientHeight,
boxW = box.offsetWidth,
boxH = box.offsetHeight;
box.style.left = (winW - boxW) / 2 + 'px';
box.style.top = (winH - boxH) / 2 + 'px';
</script>
</body>
</html>
这种方式是通过js来实现的。
方案六
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>方案六
</title>
<style>
*{
margin: 0;
padding:0;
}
html,
body{
position: relative;
height:100%;
overflow: hidden;
}
.content{
display: table-cell;
vertical-align: middle;
text-align: center;
width: 700px;
height: 700px;
background-color: aqua;
}
.box{
display: inline-block;
box-sizing: border-box;
width: 100px;
height: 50px;
line-height: 50px;
text-align: center;
font-size: 16px;
background-color: pink;
}
</style>
</head>
<body>
<div class="content">
<div class="box" id="box">
方案六
</div>
</div>
</body>
</html>
这种方式要有具体宽高。这种方式虽然可以水平垂直居中，但项目中很少有人用。
