Bootstrap برای ایجاد پیغام های هشدار از پیش تعریف شده یک راه ساده ارائه داده است :
هشدارها توسط کلاس .alert، به همراه یکی از چهار کلاس متنی .alert-success، .alert-info، .alert-warningو یا .alert-dangerایجاد می شوند.
<!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="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h2>Alerts</h2>
<div class="alert alert-success">
<strong>Success!</strong> This alert box could indicate a successful or positive action.
</div>
<div class="alert alert-info">
<strong>Info!</strong> This alert box could indicate a neutral informative change or action.
</div>
<div class="alert alert-warning">
<strong>Warning!</strong> This alert box could indicate a warning that might need attention.
</div>
<div class="alert alert-danger">
<strong>Danger!</strong> This alert box could indicate a dangerous or potentially negative action.
</div>
</div>
</body>
</html>
بستن هشدارها
برای بستن پیغام هشدار کلاس "class="close و "data-dismiss="alert را به عنصر link و یا button اضافه کنید:
<!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="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h2>Alerts</h2>
<p>The a element with class="close" and data-dismiss="alert" is used to close the alert box.</p>
<div class="alert alert-success">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Success!</strong> This alert box could indicate a successful or positive action.
</div>
<div class="alert alert-info">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Info!</strong> This alert box could indicate a neutral informative change or action.
</div>
<div class="alert alert-warning">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Warning!</strong> This alert box could indicate a warning that might need attention.
</div>
<div class="alert alert-danger">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Danger!</strong> This alert box could indicate a dangerous or potentially negative action.
</div>
</div>
</body>
</html>
نکته :
خصوصیت *-aria و times&
برای بهبود دسترسی افرادی که از screen reader ها استفاده می کنند، باید در زمان ایجاد close button (دکمه بستن) از خصوصیت "aria-label="close استفاده کنید.
Times; ( x )& یک موجودیت در HTML است که برای ایجاد close button (دکمه های بستن)، مقدم تر از حرف "x" است.
هشدارهای متحرک
کلاس های .fadeو .in زمانیکه یک پیغام هشدار در حال بسته شدن است، یک افکت محو شدگی روی آن اعمال می کند.
<!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="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</head>
<body>
<div class="container">
<h2>Alerts</h2>
<p>The .fade and .in classes adds a fading effect when closing the alert message.</p>
<div class="alert alert-success fade in">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Success!</strong> This alert box could indicate a successful or positive action.
</div>
<div class="alert alert-info fade in">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Info!</strong> This alert box could indicate a neutral informative change or action.
</div>
<div class="alert alert-warning fade in">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Warning!</strong> This alert box could indicate a warning that might need attention.
</div>
<div class="alert alert-danger fade in">
<a href="#" class="close" data-dismiss="alert" aria-label="close">×</a>
<strong>Danger!</strong> This alert box could indicate a dangerous or potentially negative action.
</div>
</div>
</body>
</html>