Bootstrap4 模态框

<!-- 按钮：用于打开模态框 -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#myModal">
  打开模态框
</button>
 
<!-- 模态框 -->
<div class="modal fade" id="myModal">
  <div class="modal-dialog">
    <div class="modal-content">
 
      <!-- 模态框头部 -->
      <div class="modal-header">
        <h4 class="modal-title">模态框头部</h4>
        <button type="button" class="close" data-dismiss="modal">&times;</button>
      </div>
 
      <!-- 模态框主体 -->
      <div class="modal-body">
        模态框内容..
      </div>
 
      <!-- 模态框底部 -->
      <div class="modal-footer">
        <button type="button" class="btn btn-secondary" data-dismiss="modal">关闭</button>
      </div>
 
    </div>
  </div>
</div>

<div class="modal-dialog modal-sm">
<div class="modal-dialog modal-lg">