在线运行代码 - 菜鸟教程

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>菜鸟教程(cainiaoplay.com)</title>
<style>div#main{
	width:220px;
	height:300px;
	border:1px solid black;
	display:flex;
	align-items:center;
}
div#main div{
	flex: 1;
}
</style>
</head>
<body>

<div id="main">
	<div style="background-color:coral;">RED</div>
  	<div style="background-color:lightblue;">BLUE</div>  
  	<div style="background-color:lightgreen;">Green div with more content.</div>
</div>
<p>点击“尝试一下”按钮设置 alignItems 属性的值为 "flex-start"。</p>
<button onclick="myFunction()">尝试一下</button>
<script>
function myFunction(){
	document.getElementById("main").style.alignItems = "flex-start";
}
</script>
<p><b>注意：</b>Safari 不支持 alignItems 属性。</p>

</body>
</html>
源代码

动行结果
