1、导航案例：

  1. <head>
  2.     <meta charset="UTF-8">
  3.     <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
  4.     <link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css"
  5.         integrity="sha384-ggOyR0iXCbMQv3Xipma34MD+dH/1fQ784/j6cY/iJTQUOhcWr7x9JvoRxT2MZw1T" crossorigin="anonymous">
  6.     <title></title>
  7.     <style>
  8.         .navbarBg{
  9.             min-height: 4rem;
  10.             background: #563d7c;
  11.             box-shadow: 0 0.5rem 1rem rgba(0,0,0,.05), inset 0 -1px 0 rgba(0,0,0,.1);
  12.         }
  13.         .svgSize{
  14.             width: 1rem;
  15.             height: 1rem;
  16.             vertical-align: text-top;
  17.             /* vertical-align: text-top;：文字顶线对齐 */
  18.         }
  19.         .navbarBg .navbar-nav .nav-link{
  20.             color: #cbbde2;
  21.         }
  23.         #docsNav .nav{
  24.             display: block;
  25.         }
  26.         #docsNav .nav li{
  27.             padding: 0.25rem 1.5rem;
  28.         }
  29.         #docsNav .nav li a{
  30.             color: rgba(0, 0, 0, 0.65);
  31.         }
  32.     </style>
  33. </head>
  35. <body>
  36.     <header class="navbar navbar-expand navbar-dark navbarBg flex-column flex-md-row"><!-- navbarBg:驼峰式自己定义的class名 -->
  37.         <!-- flex-md-row：可在俩行中显示 -->
  38.         <a href="#" class="navbar-brand mr-md-2">
  39.             <img src="http://getbootstrap.com/docs/4.1/assets/brand/bootstrap-solid.svg" alt="" width="36" class="border rounded">
  40.         </a>
  41.         <!-- border rounded：给了边框和圆角 -->
  42.         <ul class="navbar-nav">
  43.             <li class="nav-item">
  44.                 <a href="#" class="nav-link">Home</a>
  45.             </li>
  46.             <li class="nav-item">
  47.                 <a href="#" class="nav-link">Documentation</a>
  48.             </li>
  49.             <li class="nav-item">
  50.                 <a href="#" class="nav-link">Examples</a>
  51.             </li>
  52.             <li class="nav-item">
  53.                 <a href="#" class="nav-link">Themes</a>
  54.             </li>
  55.             <li class="nav-item">
  56.                 <a href="#" class="nav-link">Expo</a>
  57.             </li>
  58.             <li class="nav-item">
  59.                 <a href="#" class="nav-link">Blog</a>
  60.             </li>
  61.         </ul>
  63.         <ul class="navbar-nav ml-md-auto d-none d-md-flex">
  64.             <li class="nav-item dropdown">
  65.                 <a href="#" class="nav-link dropdown-toggle" data-toggle="dropdown">v4.3</a>
  66.                 <div class="dropdown-menu dropdown-menu-right"><!-- dropdown-menu-right:菜单右对齐 -->
  67.                     <a href="#" class="dropdown-item active">Latest (4.3.x)</a>
  68.                     <a href="#" class="dropdown-item">v4.2.1</a>
  69.                     <a href="#" class="dropdown-item">v4.0.0</a>
  70.                     <div class="dropdown-divider"></div>
  71.                     <a href="#" class="dropdown-item">v4 Alpha 6</a>
  72.                     <a href="#" class="dropdown-item">v3.4.1</a>
  73.                     <a href="#" class="dropdown-item">v3.3.7</a>
  74.                     <a href="#" class="dropdown-item">v2.3.2</a>
  75.                     <div class="dropdown-divider"></div>
  76.                     <a href="#" class="dropdown-item">All versions</a>
  77.                 </div>
  78.             </li>
  80.             <li class="nav-item">
  81.                 <a href="#" class="nav-link">
  82.                     <svg xmlns="http://www.w3.org/2000/svg" class="svgSize" viewBox="0 0 512 499.36" role="img" focusable="false">
  83.                         <title>GitHub</title>
  84.                         <path fill="currentColor" fill-rule="evenodd" d="M256 0C114.64 0 0 114.61 0 256c0 113.09 73.34 209 175.08 242.9 12.8 2.35 17.47-5.56 17.47-12.34 0-6.08-.22-22.18-.35-43.54-71.2 15.49-86.2-34.34-86.2-34.34-11.64-29.57-28.42-37.45-28.42-37.45-23.27-15.84 1.73-15.55 1.73-15.55 25.69 1.81 39.21 26.38 39.21 26.38 22.84 39.12 59.92 27.82 74.5 21.27 2.33-16.54 8.94-27.82 16.25-34.22-56.84-6.43-116.6-28.43-116.6-126.49 0-27.95 10-50.8 26.35-68.69-2.63-6.48-11.42-32.5 2.51-67.75 0 0 21.49-6.88 70.4 26.24a242.65 242.65 0 0 1 128.18 0c48.87-33.13 70.33-26.24 70.33-26.24 14 35.25 5.18 61.27 2.55 67.75 16.41 17.9 26.31 40.75 26.31 68.69 0 98.35-59.85 120-116.88 126.32 9.19 7.9 17.38 23.53 17.38 47.41 0 34.22-.31 61.83-.31 70.23 0 6.85 4.61 14.81 17.6 12.31C438.72 464.97 512 369.08 512 256.02 512 114.62 397.37 0 256 0z"></path>
  85.                     </svg>
  86.                 </a>
  87.             </li>
  88.             <li class="nav-item">
  89.                 <a href="#" class="nav-link">
  90.                     <svg xmlns="http://www.w3.org/2000/svg" class="svgSize" viewBox="0 0 512 499.36" role="img" focusable="false">
  91.                         <title>GitHub</title>
  92.                         <path fill="currentColor" fill-rule="evenodd" d="M256 0C114.64 0 0 114.61 0 256c0 113.09 73.34 209 175.08 242.9 12.8 2.35 17.47-5.56 17.47-12.34 0-6.08-.22-22.18-.35-43.54-71.2 15.49-86.2-34.34-86.2-34.34-11.64-29.57-28.42-37.45-28.42-37.45-23.27-15.84 1.73-15.55 1.73-15.55 25.69 1.81 39.21 26.38 39.21 26.38 22.84 39.12 59.92 27.82 74.5 21.27 2.33-16.54 8.94-27.82 16.25-34.22-56.84-6.43-116.6-28.43-116.6-126.49 0-27.95 10-50.8 26.35-68.69-2.63-6.48-11.42-32.5 2.51-67.75 0 0 21.49-6.88 70.4 26.24a242.65 242.65 0 0 1 128.18 0c48.87-33.13 70.33-26.24 70.33-26.24 14 35.25 5.18 61.27 2.55 67.75 16.41 17.9 26.31 40.75 26.31 68.69 0 98.35-59.85 120-116.88 126.32 9.19 7.9 17.38 23.53 17.38 47.41 0 34.22-.31 61.83-.31 70.23 0 6.85 4.61 14.81 17.6 12.31C438.72 464.97 512 369.08 512 256.02 512 114.62 397.37 0 256 0z"></path>
  93.                     </svg>
  94.                 </a>
  95.             </li>
  96.             <li class="nav-item">
  97.                 <a href="#" class="nav-link">
  98.                     <svg xmlns="http://www.w3.org/2000/svg" class="svgSize" viewBox="0 0 512 499.36" role="img" focusable="false">
  99.                         <title>GitHub</title>
  100.                         <path fill="currentColor" fill-rule="evenodd" d="M256 0C114.64 0 0 114.61 0 256c0 113.09 73.34 209 175.08 242.9 12.8 2.35 17.47-5.56 17.47-12.34 0-6.08-.22-22.18-.35-43.54-71.2 15.49-86.2-34.34-86.2-34.34-11.64-29.57-28.42-37.45-28.42-37.45-23.27-15.84 1.73-15.55 1.73-15.55 25.69 1.81 39.21 26.38 39.21 26.38 22.84 39.12 59.92 27.82 74.5 21.27 2.33-16.54 8.94-27.82 16.25-34.22-56.84-6.43-116.6-28.43-116.6-126.49 0-27.95 10-50.8 26.35-68.69-2.63-6.48-11.42-32.5 2.51-67.75 0 0 21.49-6.88 70.4 26.24a242.65 242.65 0 0 1 128.18 0c48.87-33.13 70.33-26.24 70.33-26.24 14 35.25 5.18 61.27 2.55 67.75 16.41 17.9 26.31 40.75 26.31 68.69 0 98.35-59.85 120-116.88 126.32 9.19 7.9 17.38 23.53 17.38 47.41 0 34.22-.31 61.83-.31 70.23 0 6.85 4.61 14.81 17.6 12.31C438.72 464.97 512 369.08 512 256.02 512 114.62 397.37 0 256 0z"></path>
  101.                     </svg>
  102.                 </a>
  103.             </li>
  104.             <li class="nav-item">
  105.                 <a href="#" class="nav-link">
  106.                     <svg xmlns="http://www.w3.org/2000/svg" class="svgSize" viewBox="0 0 512 499.36" role="img" focusable="false">
  107.                         <title>GitHub</title>
  108.                         <path fill="currentColor" fill-rule="evenodd" d="M256 0C114.64 0 0 114.61 0 256c0 113.09 73.34 209 175.08 242.9 12.8 2.35 17.47-5.56 17.47-12.34 0-6.08-.22-22.18-.35-43.54-71.2 15.49-86.2-34.34-86.2-34.34-11.64-29.57-28.42-37.45-28.42-37.45-23.27-15.84 1.73-15.55 1.73-15.55 25.69 1.81 39.21 26.38 39.21 26.38 22.84 39.12 59.92 27.82 74.5 21.27 2.33-16.54 8.94-27.82 16.25-34.22-56.84-6.43-116.6-28.43-116.6-126.49 0-27.95 10-50.8 26.35-68.69-2.63-6.48-11.42-32.5 2.51-67.75 0 0 21.49-6.88 70.4 26.24a242.65 242.65 0 0 1 128.18 0c48.87-33.13 70.33-26.24 70.33-26.24 14 35.25 5.18 61.27 2.55 67.75 16.41 17.9 26.31 40.75 26.31 68.69 0 98.35-59.85 120-116.88 126.32 9.19 7.9 17.38 23.53 17.38 47.41 0 34.22-.31 61.83-.31 70.23 0 6.85 4.61 14.81 17.6 12.31C438.72 464.97 512 369.08 512 256.02 512 114.62 397.37 0 256 0z"></path>
  109.                     </svg>
  110.                 </a>
  111.             </li>
  112.         </ul>
  113.         <a href="#" class="btn btn-outline-warning ml-lg-3 d-none d-lg-block">Download</a><!-- d-none d-lg-block：默认不显示，在lg以上才显示 -->
  115.     </header>
  117.     <!-- 搜索框 -->
  118.     <div class="container-fluid">    <!-- container-fluid：？？？？ -->
  119.         <div class="row">
  120.             <div class="col-md-3 col-xl-2 border-right border-bottom">
  121.                 <form action="#" class="d-flex py-3 px-1">
  122.                     <input type="search" class="form-control" placeholder="Search...">
  123.                     <button type="button" class="btn p-0 ml-3 d-md-none" data-toggle="collapse" data-target="#docsNav">
  124.                         <!-- 使用的是svg来表示三条杠 -->
  125.                         <svg xmlns="http://www.w3.org/2000/svg" width="30" height="30" viewBox="0 0 30 30" role="img" focusable="false">
  126.                             <title>Menu</title>
  127.                             <path stroke="currentColor" stroke-linecap="round" stroke-miterlimit="10" stroke-width="2" d="M4 7h22M4 15h22M4 23h22"></path>
  128.                         </svg>
  129.                     </button>
  130.                 </form>
  132.                 <div class="collapse" id="docsNav">
  133.                     <div>
  134.                         <h6 class="px-4 pt-2">
  135.                             <a href="#" class="text-dark">Components</a>
  136.                         </h6>
  137.                         <ul class="nav">
  138.                             <li><a href="#">Alerts</a></li>
  139.                             <li><a href="#">Badge</a></li>
  140.                             <li><a href="#">Buttons</a></li>
  141.                             <li><a href="#">Card</a></li>
  142.                             <li><a href="#">Collapse</a></li>
  143.                             <li><a href="#">Dropdown</a></li>
  144.                             <li><a href="#">Froms</a></li>
  145.                         </ul>
  146.                     </div>
  147.                 </div>
  148.             </div>
  149.             <div class="col-md-9 col-xl-10"></div><!-- 右侧自己写 -->
  150.         </div>
  151.     </div>
  155.     <script src="https://code.jquery.com/jquery-3.3.1.slim.min.js"
  156.         integrity="sha384-q8i/X+965DzO0rT7abK41JStQIAqVgRVzpbzo5smXKp4YfRvH+8abtTE1Pi6jizo"
  157.         crossorigin="anonymous"></script>
  158.     <script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.7/umd/popper.min.js"
  159.         integrity="sha384-UO2eT0CpHqdSJQ6hJty5KVphtPhzWj9WO1clHTMGa3JDZwrnQq4sF86dIHNDz0W1"
  160.         crossorigin="anonymous"></script>
  161.     <script src="https://stackpath.bootstrapcdn.com/bootstrap/4.3.1/js/bootstrap.min.js"
  162.         integrity="sha384-JjSmVgyd0p3pXB1rRibZUAYoIIy6OrQ6VrjIEaFf/nJGzIxFDsf4x0xIM+B07jRM"
  163.         crossorigin="anonymous"></script>
  164. </body>

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