Just append a div with that class to body, then remove it when you’re done:
// Show the backdrop
$('<div class="modal-backdrop"></div>').appendTo(document.body);
// Remove it (later)
$(".modal-backdrop").remove();
Live Example:
$("input").click(function() {
var bd = $('<div class="modal-backdrop"></div>');
bd.appendTo(document.body);
setTimeout(function() {
bd.remove();
}, 2000);
});
<link href="https://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.min.css" rel="stylesheet" type="text/css" />
<script src="https://code.jquery.com/jquery.min.js"></script>
<script src="https://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/js/bootstrap.min.js"></script>
<p>Click the button to get the backdrop for two seconds.</p>
<input type="button" value="Click Me">