如何在模态框(modal)中将div定位至表格右下角相邻位置

你不需要使用fixed定位，仅调整Bootstrap栅格结构即可实现需求，核心是利用flex对齐规则让右侧信息块和表格底部对齐：

• 给modal-body内部新增一层<div class="row align-items-end">容器，将原有的表格列（col-md-10）和信息列（col-md-2）都放入这个容器中。align-items-end是Bootstrap内置的flex工具类，会让行内所有列的底部自动对齐，右侧信息块就会自然贴合在表格右下角相邻位置。
• 小屏幕下（宽度小于768px），col-md-*的栅格规则会自动失效，两个列都会变为100%宽度，表格占满整行后信息块紧随在表格下方展示，完全符合你要求的小屏布局。

如果需要调整信息块和表格的水平间距，给右侧col-md-2添加自定义的padding或margin属性调整即可。

完整修改后代码 #

<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.min.css" integrity="sha384-Vkoo8x4CGsO3+Hhxv8T/Q5PaXtkKtu6ug5TOeNV6gBiFeWPGFN9MuhOf23Q9Ifjh" crossorigin="anonymous">

<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalLong">
Launch demo modal
</button>
<!-- Modal -->
<div class="modal fade" id="exampleModalLong" tabindex="-1" role="dialog" aria-labelledby="exampleModalLongTitle" aria-hidden="true">
   <div class="modal-dialog modal-lg" role="document">
      <div class="modal-content">
         <div class="modal-header">
            <h5 class="modal-title" id="exampleModalLongTitle">Modal title</h5>
            <button type="button" class="close" data-dismiss="modal" aria-label="Close">
            <span aria-hidden="true">&times;</span>
            </button>
         </div>
         <div class="modal-body">
            <!-- 新增带底部对齐的行容器 -->
            <div class="row align-items-end">
               <div class="col-md-10">
                  <div class="table-responsive">
                     <table id="items-job-payments-modal-table" class="table table-striped">
                        <thead>
                           <tr>
                              <th>Date</th>
                              <th>Amount</th>
                              <th>Type</th>
                              <th>Note</th>
                           </tr>
                        </thead>
                        <tbody>
                           <tr>
                              <td>Example</td>
                              <td>Example</td>
                              <td>Example</td>
                              <td>Example</td>
                           </tr>
                        </tbody>
                     </table>
                  </div>
               </div>
               <div class="col-md-2">
                  <div>
                     <div class="form-group">
                        <label id="">Total Cost</label>
                        <label id="">10</label>
                     </div>
                     <div class="form-group">
                        <label id="">Balance</label>
                        <label id="">5</label>
                     </div>
                  </div>
               </div>
            </div>
         </div>
         <div class="modal-footer">
            <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
            <button type="button" class="btn btn-primary">Save changes</button>
         </div>
      </div>
   </div>
</div>
<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/popper.js@1.16.0/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>

内容的提问来源于stack exchange，提问作者Mohamed