มีปัญหาในการใช้งาน SweetAlert ครับ ตอน foreach ปุ่มครับ

<div class="row">
            <div class="col-xs-12">
              <div class="box">
                <div class="box-header">
                    <h3 class="box-title">Slider List</h3>
                   
                </div><!-- /.box-header -->
                <div class="box-body table-responsive no-padding table-responsive">
                  <table id="datatable"  class="table table-bordered dataTable no-footer ">
                    <thead>
                    <tr style="background-color: #79dde66e;">
                      <th >NO</th>
                      <th class="text-center">title</th>
                      <th class="text-center">img</th>
                      <th class="text-center">description</th>
                      <th class="text-center">lang</th>
                      <th class="text-center">start date</th>
                      <th class="text-center">end date</th>
                      <th class="text-center">Edit</th>
                      <th class="text-center">Delete</th>    
                    </tr>
                    </thead>
                    <?php 
                       $this->db->order_by('id','desc');
                       $data = $this->db->get('mcl_sliders')->result_array(); 
                    ?>
                     <?php foreach ($data as $key => $data){ ?>
                    
                  
                    <tr>
                      <td style="width: 2%"></td>
                      <td style="width: 10%"><?php echo $data['title']; ?></td>
                      <td style="width: 5%">
                        <?php if (!empty($data['file_name'])): ?>
                            <img src=" <?php echo ("uploads/".$data['file_name']) ?>" alt="" style="width: 100px; height: 100px;">

                        <?php else: ?>
                             <img src=" <?php echo ("uploads/access.png") ?>" alt="" style="width: 100px; height: 100px;">

                        <?php endif ?>

                        
                       </td>
                      <td style="width: 15%"><?php echo $data['description']; ?></td>
                      <?php 
                        $langlist = $this->db->get_where('mcl_langs',['code'=>$data['lang']])->result_array();
                           foreach ($langlist as $key => $langlist) {   
                        ?>

                     <td style="width: 5%" class="text-center"><?php echo $langlist['name']; ?></td>
                      <?php } ?>
                     
                      
                      <td style="width: 8%"><?php echo $data['start_date']; ?></td>
                      <td style="width: 8%"><?php echo $data['end_date']; ?></td>
                      <td style="width: 5%" class="text-center"><a href="editslider/?id=<?php echo $data['id'];?>"><button class="btn btn-warning">Edit</button></a></td>
                     <th style="width: 5%" class="text-center">
                       <form action="#" method="post" onsubmit="return" >
                         <input type="hidden" name="id" value="<?php echo $data['id']; ?>">
                         <button class="btn btn-danger sweet-3" type="submit" onclick="myFunction()"  >Delete</button>
                       </form>
                     </th>
                    </tr>

                  <?php } ?>
                  </table>
                  
                </div><!-- /.box-body -->
                <div class="box-footer clearfix">
                    <?php echo $this->pagination->create_links(); ?>
                </div>
              </div><!-- /.box -->
            </div>
        </div>

<script>
document.querySelector('.sweet-3').onclick = function(){
        swal("Good job!", "You clicked the button!", "success");
      };


</script>