$('.closeall').click(function () {
          $('.collapse').collapse('hide');
});


  $('.openall').click(function () {
        $('.collapse').collapse('show');
  });

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" >

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>

 <a class="btn btn-primary openall" href="#">open all</a> <a class="btn btn-danger closeall" href="#">close all</a>
<hr>

<div class="panel-group" id="accordion" role="tablist" aria-multiselectable="true">
  <div class="panel panel-default">
    <div class="panel-heading" role="tab" id="headingOne">
      <h4 class="panel-title">
        <a role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseOne" aria-expanded="false" aria-controls="collapseOne">
          Collapsible Group Item #1
        </a>
      </h4>
    </div>
    <div id="collapseOne" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingOne">
      <div class="panel-body">
        #1 Expanded
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading" role="tab" id="headingTwo">
      <h4 class="panel-title">
        <a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseTwo" aria-expanded="false" aria-controls="collapseTwo">
          Collapsible Group Item #2
        </a>
      </h4>
    </div>
    <div id="collapseTwo" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingTwo">
      <div class="panel-body">
          #2 Expanded
      </div>
    </div>
  </div>
  <div class="panel panel-default">
    <div class="panel-heading" role="tab" id="headingThree">
      <h4 class="panel-title">
        <a class="collapsed" role="button" data-toggle="collapse" data-parent="#accordion" href="#collapseThree" aria-expanded="false" aria-controls="collapseThree">
          Collapsible Group Item #3
        </a>
      </h4>
    </div>
    <div id="collapseThree" class="panel-collapse collapse" role="tabpanel" aria-labelledby="headingThree">
      <div class="panel-body">
         #3 Expanded
      </div>
    </div>
  </div>
</div>

<div>
    <div class="container">
        <a class="btn btn-default openall" href="#">open all</a> <a class="btn btn-default closeall" href="#">close all</a>
        <hr>
       <div class="panel-group" id="accordion-demo" role="tablist" aria-multiselectable="true">
                <div class="panel panel-default">
                    <div class="panel-heading" role="tab" id="headingOne">
                        <h4 class="panel-title">
                            <a role="button" class="panel-title" data-toggle="collapse" data-parent="#accordion-demo" href="#prerequisites" aria-expanded="true" aria-controls="prerequisites">
                                Collapsible Group Item #1
                            </a>
                        </h4>
                    </div>
                    <div id="prerequisites" class="panel-collapse collapse in" role="tabpanel" aria-labelledby="prerequisites">
                        <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" role="tab" id="headingTwo">
                        <h4 class="panel-title">
                            <a class="collapsed panel-title" role="button" data-toggle="collapse" data-parent="#accordion-demo" href="#addwizard" aria-expanded="false" aria-controls="addwizard">
                                Collapsible Group Item #2
                            </a>
                        </h4>
                    </div>
                    <div id="addwizard" class="panel-collapse collapse" role="tabpanel" aria-labelledby="addwizard">
                        <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" role="tab" id="headingThree">
                        <h4 class="panel-title">
                            <a class="collapsed panel-title" role="button" data-toggle="collapse" data-parent="#accordion-demo" href="#adjusthtml" aria-expanded="false" aria-controls="adjusthtml">
                                Collapsible Group Item #3
                            </a>
                        </h4>
                    </div>
                    <div id="adjusthtml" class="panel-collapse collapse" role="tabpanel" aria-labelledby="adjusthtml">
                        <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>

        </div>
    </div>
    </div>
</div>

----javascript---code

$('.closeall').click(function () {
        $('.panel-collapse.in')
          .collapse('hide');
    });
    $('.openall').click(function () {
        $('.panel-collapse:not(".in")')
          .collapse('show');
    });

这在你给的codepen中为我工作。

这在bootstrap 5中对我有效

$(".closeall").click(function () {
    $(".collapse").removeClass("show");
});
$(".openall").click(function () {
    $(".collapse").addClass("show");
});

bootstrap 5.2文档是正确的，但我还是花了几次尝试才让它正常工作。似乎你必须停止在配置中切换每个可折叠：

$(".closeall").on('click', function () {
    $('#myAccordion .collapse').each(function(){
        new bootstrap.Collapse(this,{ toggle: false }).hide();
    });
});
$(".openall").on('click', function () {
    $('#myAccordion .collapse').each(function(){
        new bootstrap.Collapse(this,{ toggle: false }).show();
    });
});

如果省略{ toggle：false }不管你调用什么函数，它总是会切换每个可折叠的。