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> <style> .border { display: inline-block; width: 70px; height: 70px; margin: 6px; } </style> </head> <body> <div class="container"> <h2>边框</h2> <p>使用 border 类可以添加或移除边框:</p> <span class="border"></span> <span class="border border-0"></span> <span class="border border-top-0"></span> <span class="border border-right-0"></span> <span class="border border-bottom-0"></span> <span class="border border-left-0"></span> </div> </body> </html>
运行结果