클래스(.class)명 검사해서 처리하기

<script type="text/javascript">
$(document).ready(function() {
	var hasClass = "off";
	$("div > ul > li").each(function() {
		if($(this).hasClass("active")) {
			hasClass = "on";
		}
	});
	if(hasClass == "off") {
		$("div > ul > li").first().addClass("active");
	}
});
</script>

<div class="col-md-5">
	<ul class="nav nav-tabs nav-pills nav-stacked" role="tablist">
		<li><a href="#">Home</a></li>
		<li><a href="#">Profile</a></li>
		<li><a href="#">Messages</a></li>
	</ul>
</div>