<meta name="viewport" content="width=device-width, initial-scale=1">

<link rel="stylesheet" href="/static/lib/bootstrap/4.0.0/css/bootstrap.min.css">

<script src="/static/lib/jquery/3.3.1/jquery.min.js"></script>

<script src="/static/lib/bootstrap/4.0.0/js/bootstrap.min.js"></script>

​

<div class="container">

  <h1>水平居中</h1>

  <p>使用 .mx-auto 类来设置居中对齐</p>

  <div class="mx-auto bg-warning" style="width:150px">居中</div>

</div>

​