bootstrap----04折叠

    <!-- 1.基础      -->
    <!-- data-toggle:切换作用,href:关联作用,collapse默认是 hide属性，显示属性是show -->
    <button href="#collapseId" data-toggle="collapse">展开</button>
    <div class="collapse border" id="collapseId">你好明天，明天你好吗</div>



    <!-- 2.多个折叠菜单功能 -->
    <button href=".multi-collapse" data-toggle="collapse">按钮</button>
    <div class="collapse multi-collapse border" id="collapseId1">你好明天，明天你好吗1</div>
    <div class="collapse multi-collapse border" id="collapseId2">你好明天，明天你好吗2</div>


    <!-- 3.手风琴 -->
    <div class="accordion" id="accordion">
      <div class="card">
        <button class="" style="border:0px;" href="#collapseId1" data-toggle="collapse">按钮1</button>
        <div class="collapse" id="collapseId1" data-parent="#accordion">123</div>
      </div>
      <div class="card">
        <button class="" style="border:0px;" href="#collapseId2" data-toggle="collapse">按钮2</button>
        <div class="collapse" id="collapseId2" data-parent="#accordion">123</div>
      </div>
      <div class="card">
        <button class="" style="border:0px;" href="#collapseId3" data-toggle="collapse">按钮3</button>
        <div class="collapse" id="collapseId3" data-parent="#accordion">123</div>
      </div>