jquery dynamically adds and deletes table row special effects_jquery

The code for adding and deleting tables based on jQuery is a special effect code for dynamically adding and deleting table rows. Share it with everyone for your reference. The details are as follows:
The screenshot of the running effect is as follows:

The specific code is as follows:

html code:

<div style="width:720px;margin:20px auto;">
   <table id="tab11" style="display: none">
     <tbody>
       <tr>
         <td height="30" align="center">
           <input type="text" name="NO" size="2" value="1" />
         </td>
         <td align="center">
           <input type="text" name="start_end_time" />
         </td>
         <td align="center">
           <input type="text" name="unit_department" />
         </td>
         <td align="center">
           <input type="text" name="post" />
         </td>
         <td>
           <input type="button" id="Button1" onclick="deltr(this)" value="删行" />
         </td>
       </tr>
     </tbody>
   </table>
   <input type="button" id="btn_addtr" value="增行" />
   <table id="dynamicTable" width="700" border="0" cellspacing="0" cellpadding="0">
     <thead>
       <tr>
         <td height="30" align="center" bgcolor="#CCCCCC">ID</td>
         <td align="center" bgcolor="#CCCCCC">起止时间</td>
         <td align="center" bgcolor="#CCCCCC">单位/部门</td>
         <td align="center" bgcolor="#CCCCCC">职位</td>
         <td></td>
       </tr>
     </thead>
     <tbody>
       <tr>
         <td height="30" align="center">
           <input type="text" name="NO" size="2" value="1" />
         </td>
         <td align="center">
           <input type="text" name="start_end_time" />
         </td>
         <td align="center">
           <input type="text" name="unit_department" />
         </td>
         <td align="center">
           <input type="text" name="post" />
         </td>
         <td>
           <input type="button" id="Button2" onclick="deltr(this)" value="删行" />
         </td>
       </tr>
     </tbody>
   </table>
 </div>

js code:

$(function () {
      var show_count = 20;  //要显示的条数
      var count = 1;  //递增的开始值，这里是你的ID
      $("#btn_addtr").click(function () {
 
        var length = $("#dynamicTable tbody tr").length;
        //alert(length);
        if (length < show_count)  //点击时候，如果当前的数字小于递增结束的条件
        {
          $("#tab11 tbody tr").clone().appendTo("#dynamicTable tbody");  //在表格后面添加一行
          changeIndex();//更新行号
        }
      });
 
 
    });
    function changeIndex() {
      var i = 1;
      $("#dynamicTable tbody tr").each(function () { //循环tab tbody下的tr
        $(this).find("input[name='NO']").val(i++);//更新行号
      });
    }
 
    function deltr(opp) {
      var length = $("#dynamicTable tbody tr").length;
      //alert(length);
      if (length <= 1) {
        alert("至少保留一行");
      } else {
        $(opp).parent().parent().remove();//移除当前行
        changeIndex();
      }
    }

I hope this article will be helpful to everyone in learning javascript and programming.