单行居中，多行居左，超过两行用省略号
<!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>Document</title>
<style>
* {
margin: 0;
padding: 0;
}
h2 em {
position: relative;
font-style: normal;
text-align: left;
overflow: hidden;
text-overflow: ellipsis;
display: -webkit-box;
-webkit-line-clamp: 2;
-webkit-box-orient: vertical;
}
.container {
320px;
padding: 0 10px;
margin: 10px auto;
background: #ddd;
}
.container p {
display: inline-block;
text-align: center;
}
h2 {
text-align: center;
padding: 10px 0;
}
</style>
</head>
<body>
<div class="container">
<h2>
<p>
<em>我是单行标题居中</em>
</p>
</h2>
<h2>
<p>
<em>我是两行标题两行标题两行标题居左</em>
</p>
</h2>
<h2>
<p>
<em>我是超过两行的标题最后点号省略我是超过两行的标题最后点号省略我是超过两行的标题最后点号省略省略省略</em>
</p>
</h2>
</div>
</body>
</html>