collapse

<!DOCTYPE html>
<html lang="en">
<head>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css">
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap-theme.min.css">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js"></script>
<script type="text/javascript">
$(document).ready(function(){<!--from   w  w w .  j av  a2s  . c o  m-->
    $(".btn").click(function(){
        $("#toggleDemo").collapse('toggle');
    });
});
</script>
<style type="text/css">
p{
    background: #F9F9F9;
    border: 1px solid #E1E1E8;
    margin: 10px 0;
    padding: 8px;
}
.bs-example{
  margin: 20px;
}
</style>
</head>
<body>
<div class="bs-example">
    <!-- Trigger Button HTML -->
    <input type="button" class="btn btn-primary" value="Toggle Button">
    <!-- Collapsible Element HTML -->
    <div id="toggleDemo" class="collapse in"><p>
    this is a test. this is a test. this is a test.
    this is a test. this is a test. this is a test.
    this is a test. this is a test. this is a test.
    Click on the <b>Toggle Button</b> button to see the effect.</p></div>
</div>
</body>
</html>