<!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>
.box{
/* 1设置父元素为flex容器：加上flex属性值 */
display: flex; /* 定义元素是一个flex容器 */
width: 600px;
height: 600px;
border:1px solid red;
}
.box span{
width: 150px;
height: 50px;
background-color: skyblue;
/* 3个子盒子平均分配父盒子的空间 */
flex: 1; /* 此时宽度无用 */
}
.box span:nth-child(1){
flex: 2;
}
</style>
</head>
<body>
<div class="box">
<span>1</span><span>2</span><span>3</span>
</div>
</body>
</html>