A demo of removing class by using the className JS attribute

The Code

Output

<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css">
<script type="text/javascript">
    function removeClass()
    {
        document.getElementById('class_demo').classList.remove('btn-block');
       
    }
</script>

</head>

<body>
<h3>Click on the button to remove btn-block class by JavaScript</h3>
<button class="btn btn-success btn-block" id="class_demo" onclick="removeClass()">Remove Class by JavaScript</button>

</body>
</html>