源代码 ：
点击运行
<!DOCTYPE html> <html> <head> <title>Bootstrap 实例</title> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1"> <link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/css/bootstrap.min.css"> <script src="https://cdn.staticfile.org/jquery/3.2.1/jquery.min.js"></script> <script src="https://cdn.staticfile.org/popper.js/1.15.0/umd/popper.min.js"></script> <script src="https://cdn.staticfile.org/twitter-bootstrap/4.3.1/js/bootstrap.min.js"></script> </head> <body> <div class="container mt-3"> <h2>内容排列</h2> <p>.justify-content-*-center 类根据不同屏幕设备在 flex 容器中居中显示子元素。</p> <p>重置浏览器窗口，查看效果。</p> <p><code>.justify-content-center</code>:</p> <div class="d-flex justify-content-center bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>.justify-content-sm-center</code>:</p> <div class="d-flex justify-content-sm-center bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>.justify-content-md-center</code>:</p> <div class="d-flex justify-content-md-center bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>.justify-content-lg-center</code>:</p> <div class="d-flex justify-content-lg-center bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> <p><code>.justify-content-xl-center</code>:</p> <div class="d-flex justify-content-xl-center bg-secondary mb-3"> <div class="p-2 bg-info">Flex item 1</div> <div class="p-2 bg-warning">Flex item 2</div> <div class="p-2 bg-primary">Flex item 3</div> </div> </div> </body> </html>
运行结果