Twitter bootstrap 当“折叠”处于活动状态时更改类

如何更改活动折叠的类

示例：从面板默认更改为面板危险

<div class="panel-group" id="accordion">
  <div class="panel panel-default">
    <div class="panel-heading">
      <h4 class="panel-title">
        <a data-toggle="collapse" data-parent="#accordion" href="#collapseOne">
          Collapsible Group Item #1
        </a>
      </h4>
    </div>
    <div id="collapseOne" class="panel-collapse collapse in">
      <div class="panel-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading">
      <h4 class="panel-title">
        <a data-toggle="collapse" data-parent="#accordion" href="#collapseTwo">
          Collapsible Group Item #2
        </a>
      </h4>
    </div>
    <div id="collapseTwo" class="panel-collapse collapse">
      <div class="panel-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading">
      <h4 class="panel-title">
        <a data-toggle="collapse" data-parent="#accordion" href="#collapseThree">
          Collapsible Group Item #3
        </a>
      </h4>
    </div>
    <div id="collapseThree" class="panel-collapse collapse">
      <div class="panel-body">
        Anim pariatur cliche reprehenderit, enim eiusmod high life accusamus terry richardson ad squid. 3 wolf moon officia aute, non cupidatat skateboard dolor brunch. Food truck quinoa nesciunt laborum eiusmod. Brunch 3 wolf moon tempor, sunt aliqua put a bird on it squid single-origin coffee nulla assumenda shoreditch et. Nihil anim keffiyeh helvetica, craft beer labore wes anderson cred nesciunt sapiente ea proident. Ad vegan excepteur butcher vice lomo. Leggings occaecat craft beer farm-to-table, raw denim aesthetic synth nesciunt you probably haven't heard of them accusamus labore sustainable VHS.
      </div>
    </div>
  </div>
</div>

动物保护协会的陈词滥调，埃尼姆·埃乌斯莫德的高寿命accusamus terry richardson广告鱿鱼。3狼月亮奥特餐厅，非丘比特滑板多洛早午餐。食品车奎奴亚藜。早午餐3狼月亮临时，圣塔阿利夸放了一只鸟在上面鱿鱼单一来源咖啡NullaAssumenda shoreditch等Nihil anim keffiyeh helvetica，工艺啤酒工人wes anderson cred Nesciut sapiente ea proident。纯素食主义者，屠夫副洛莫。紧身裤从工艺啤酒场到餐桌，生料牛仔布美学合成物，你可能还没听说过accusamus labore可持续VHS。
动物保护协会的陈词滥调，埃尼姆·埃乌斯莫德的高寿命accusamus terry richardson广告鱿鱼。3狼月亮奥特餐厅，非丘比特滑板多洛早午餐。食品车奎奴亚藜。早午餐3狼月亮临时，圣塔阿利夸放了一只鸟在上面鱿鱼单一来源咖啡NullaAssumenda shoreditch等Nihil anim keffiyeh helvetica，工艺啤酒工人wes anderson cred Nesciut sapiente ea proident。纯素食主义者，屠夫副洛莫。紧身裤从工艺啤酒场到餐桌，生料牛仔布美学合成物，你可能还没听说过accusamus labore可持续VHS。
动物保护协会的陈词滥调，埃尼姆·埃乌斯莫德的高寿命accusamus terry richardson广告鱿鱼。3狼月亮奥特餐厅，非丘比特滑板多洛早午餐。食品车奎奴亚藜。早午餐3狼月亮临时，圣塔阿利夸放了一只鸟在上面鱿鱼单一来源咖啡NullaAssumenda shoreditch等Nihil anim keffiyeh helvetica，工艺啤酒工人wes anderson cred Nesciut sapiente ea proident。纯素食主义者，屠夫副洛莫。紧身裤从工艺啤酒场到餐桌，生料牛仔布美学合成物，你可能还没听说过accusamus labore可持续VHS。

基于引导代码的非工作示例如下：

---

谢谢

您可以使用

显示的.bs.collapse

和

隐藏的.bs.collapse

事件：

showed.bs.collapse-当一个collapse元素 已使用户可见（将等待CSS转换到 完成）

及

hidden.bs.collapse-当一个collapse元素 已对用户隐藏（将等待CSS转换完成）

要添加和删除附加类，当页面开始时，可以检查打开的页面并在其上设置类

代码：

演示：

$('#accordion').find('.panel-default:has(".in")').addClass('panel-danger');

$('#accordion').on('shown.bs.collapse', function (e) {
   $(e.target).closest('.panel-default').addClass(' panel-danger');
}).on('hidden.bs.collapse', function (e) {
   $(e.target).closest('.panel-default').removeClass(' panel-danger');
})