Using toggle attribute of JavaScript to add / remove a class

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.toggle('btn-lg');
       
    }
</script>

</head>

<body>
<h3>Click on the button to add/remove btn-lg class by JavaScript</h3>
<button class="btn btn-info btn-lg" id="class_demo" onclick="removeClass()">Add/Remove Class by JavaScript toggle</button>

</body>
</html>