向Bootstrap 4卡添加灰色背景色
要为Bootstrap4卡添加灰色背景色，请将该卡类与bg-dark上下文类一起使用-
<div class="card bg-dark text-white">
将卡主体设置在相同的<div>类中-
<div class="card bg-dark text-white"> <div class="card-body">Hello</div> </div>
让我们看看完整的示例，向Bootstrap卡添加灰色背景色-
示例
<!DOCTYPE html>
<html lang="en">
<head>
<title>Bootstrap Example</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/css/bootstrap.min.css">
<script src="https://cdn.staticfile.org/jquery/3.3.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.0/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h2>Welcome</h2>
<div class="card bg-dark text-white">
<div class="card-body">Hello</div>
</div>
</div>
</body>
</html>