中间定宽，两边自适应布局的三种实现方法
1. 浮动加定位
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>中间定宽，两边自适应</title>
<style type="text/css">
html,body,div{
height: 100%;
}
.parent{
position: relative;
overflow: hidden;
}
.left{
float: left;
50%;
margin-left: -150px;
background-color: red;
}
.right{
float: right;
50%;
margin-right: -150px;
background-color: yellow;
}
.center{
position: absolute;
left:50%;
transform:translateX(-50%);
300px;
background-color: green;
}
.left .item{
margin-left: 150px;
}
.right .item{
margin-right: 150px;
}
</style>
</head>
<body>
<div class="parent">
<div class="left">
<div class="item"></div>
</div>
<div class="right">
<div class="item"></div>
</div>
<div class="center">
<div class="item"></div>
</div>
</div>
</body>
</html>
2. calc计算法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>中间定宽，两边自适应</title>
<style type="text/css">
html,body,div{
height: 100%;
}
.left{
calc(50% - 150px);
float: left;
background-color: red;
}
.right{
calc(50% - 150px);
float: right;
background-color: yellow;
}
.center{
300px;
float: left;
background-color: green;
}
/*也可以将这三个div设置成display:inline-block,这样就不浮动了*/
</style>
</head>
<body>
<div class="left"></div>
<div class="center"></div>
<div class="right"></div>
</body>
</html>
3. 弹性盒子法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>中间定宽，两边自适应</title>
<style type="text/css">
html,body,div{
height: 100%;
}
.parent{
display: flex;
}
.left{
flex:1;
background-color: red;
}
.right{
flex:1;
background-color: yellow;
}
.center{
300px;
background-color: green;
}
</style>
</head>
<body>
<div class="parent">
<div class="left"></div>
<div class="center"></div>
<div class="right"></div>
</div>
</body>
</html>