常用知识点：flex-grow,flex-basis,order。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Flex布局</title>
<style type="text/css">
#container {
display: flex;
}
#left,#right,#main {
min-height: 170px;
}
#left {
order: -1;
flex-basis: 200px;
background-color: red;
}
#main {
flex-grow: 1;
background-color: green;
}
#right {
flex-basis: 300px;
background-color: blue;
}
</style>
</head>
<body>
<div id="container">
<div id="left">left</div>
<div id="main">main</div>
<div id="right">right</div>
</div>
</body>
</html>
原文：https://www.cnblogs.com/Longhua-0/p/9966841.html