如何利用bootstrap做一个动态进度条

<link rel="stylesheet" href="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/css/bootstrap.min.css">
<script src="https://cdn.staticfile.org/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdn.staticfile.org/twitter-bootstrap/3.3.7/js/bootstrap.min.js"></script>

<div class="progress progress-striped active">
  <div class="progress-bar progress-bar-success" role="progressbar"
    aria-valuenow="60" aria-valuemin="0" aria-valuemax="100"
    style="width: 40%;">
    <span class="sr-only">40% 完成</span>
  </div>
</div>