Bootstrap4中，信息提示框功能的实现非常容易。而且可以使用各种类实现提示框的颜色、动画等样式。
提示框颜色：
提示框可以使用 .alert 类, 后面加上 .alert-success, .alert-info, .alert-warning, .alert-danger, .alert-primary, .alert-secondary, .alert-light 或 .alert-dark 类来实现颜色的变化:
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap4 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.1.0/css/bootstrap.min.css" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" >
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/bootstrap/4.1.0/js/bootstrap.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
</head>
<body>
<div class="container">
<h2>提示框</h2>
<p>提示框可以使用 .alert 类, 后面加上指定特定意义的颜色类来实现:</p>
<div class="alert alert-success">
<strong>成功!</strong> 指定操作成功提示信息。
</div>
<div class="alert alert-info">
<strong>信息!</strong> 请注意这个信息。
</div>
<div class="alert alert-warning">
<strong>警告!</strong> 设置警告信息。
</div>
<div class="alert alert-danger">
<strong>错误!</strong> 失败的操作
</div>
<div class="alert alert-primary">
? <strong>首选!</strong> 这是一个重要的操作信息。
</div>
<div class="alert alert-secondary">
? <strong>次要的!</strong> 显示一些不重要的信息。
</div>
<div class="alert alert-dark">
? <strong>深灰色!</strong> 深灰色提示框。
</div>
<div class="alert alert-light">
? <strong>浅灰色!</strong>浅灰色提示框。
</div>
</div>
</body>
</html>
提示框添加链接
提示框中在链接的标签上添加 alert-link 类来设置匹配提示框颜色的链接：
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap4 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.1.0/css/bootstrap.min.css" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" >
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/bootstrap/4.1.0/js/bootstrap.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
</head>
<body>
<div class="container">
<h2>提示框添加链接</h2>
<p>提示框中在链接的标签上添加 alert-link 类来设置匹配提示框颜色的链接：</p>
<div class="alert alert-success">
<strong>成功!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-info">
<strong>信息!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-warning">
<strong>警告!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-danger">
<strong>错误!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-primary">
<strong>首选!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-secondary">
<strong>次要的!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-dark">
<strong>深灰色!</strong>你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
<div class="alert alert-light">
<strong>灰色!</strong> 你应该认真阅读 <a href="#" class="alert-link">这条信息</a>。
</div>
</div>
</body>
</html>
关闭提示框
我们可以在提示框中的 div 中添加 .alert-dismissable 类，然后在关闭按钮的链接上添加 和 data-dismiss="alert" 类来设置提示框的关闭操作。
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap4 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.1.0/css/bootstrap.min.css" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" >
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/bootstrap/4.1.0/js/bootstrap.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
</head>
<body>
<div class="container">
<h2>关闭提示框</h2>
<p>我们可以在提示框中的 div 中添加 .alert-dismissable 类，然后在关闭按钮的链接上添加 class="close" 和 data-dismiss="alert" 类来设置提示框的关闭操作。</p>
<div class="alert alert-success alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>成功!</strong> 指定操作成功提示信息。
</div>
<div class="alert alert-info alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>信息!</strong> 请注意这个信息。
</div>
<div class="alert alert-warning alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>警告!</strong> 设置警告信息。
</div>
<div class="alert alert-danger alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>错误!</strong> 失败的操作。
</div>
<div class="alert alert-primary alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>首选!</strong> 这是一个重要的操作信息。
</div>
<div class="alert alert-secondary alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>次要的!</strong> 显示一些不重要的信息。
</div>
<div class="alert alert-dark alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>深灰色!</strong> 深灰色提示框。
</div>
<div class="alert alert-light alert-dismissable">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>浅灰色!</strong>浅灰色提示框。
</div>
</div>
</body>
</html>
提示: × (×) 是 HTML 实体字符，来表示关闭操作，而不是字母 "x"。
提示框动画
.fade 和 .show 类用于设置提示框在关闭时的淡出和淡入效果：
<!DOCTYPE html>
<html>
<head>
<title>Bootstrap4 实例</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://cdn.bootcss.com/bootstrap/4.1.0/css/bootstrap.min.css" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" target="_blank" >
<script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/popper.js/1.12.5/umd/popper.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
<script src="https://cdn.bootcss.com/bootstrap/4.1.0/js/bootstrap.min.js" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" ></script>
</head>
<body>
<div class="container">
<h2>提示框动画</h2>
<p>.fade 和 .show 类用于设置提示框在关闭时的淡出和淡入效果：</p>
<div class="alert alert-success alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>成功!</strong> 指定操作成功提示信息。
</div>
<div class="alert alert-info alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>信息!</strong> 请注意这个信息。
</div>
<div class="alert alert-warning alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>警告!</strong> 设置警告信息。
</div>
<div class="alert alert-danger alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>错误!</strong> 失败的操作。
</div>
<div class="alert alert-primary alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>首选!</strong> 这是一个重要的操作信息。
</div>
<div class="alert alert-secondary alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>次要的!</strong> 显示一些不重要的信息。
</div>
<div class="alert alert-dark alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>深灰色!</strong> 深灰色提示框。
</div>
<div class="alert alert-light alert-dismissable fade show">
<button type="button" class="close" data-dismiss="alert">×</button>
<strong>浅灰色!</strong>浅灰色提示框。
</div>
</div>
</body>
</html>