JavaScript實現簡單購物小表格

<table border="" cellspacing="0" cellpadding="1">
   <tr style="background-color: #0099cc;">
    <td><input type="checkbox"class="all"/></td>
    <td style="text-align: center; width: 200px;">商品</td>
    <td style="color: white; width: 70px; height: 30px; text-align: center;">價錢</td>
   </tr>
   <tr class="zuida">
    <td><input type="checkbox" class="lla"/></td>
    <td>蘋果</td>
    <td style="text-align: center;" class="zongji">8000</td>
   </tr>
   <tr  class="zuida">
    <td><input type="checkbox" class="lla"/></td>
    <td>香蕉</td>
    <td style="text-align: center;" class="zongji">5000</td>
   </tr>
   <tr  class="zuida">
    <td><input type="checkbox" class="lla"/></td>
    <td>梨子</td>
    <td style="text-align: center;" class="zongji">2000</td>
   </tr>
   <tr  class="zuida">
    <td><input type="checkbox" class="lla"/></td>
    <td>蔬菜</td>
    <td style="text-align: center;" class="zongji">2000</td>
   </tr>
   <tr>
    <td colspan="3">總價是：<span class="zongjia">0</span>元</td>
   </tr>
</table>

<script src="jquery-3.6.0.min.js" type="text/javascript" charset="utf-8"></script>
  <script type="text/javascript">
   $(function(){
     $(".all").change(function(){
      var value=$(this).prop("checked")
      $(".lla").prop("checked",value)
      zongjia()
     })
     $(".lla").click(function(){
      var chang1=$(".lla").length;
      var chang2=$(".lla:checked").length;
      if(chang1===chang2){
       $(".all").prop("checked",true)
      }else{
       $(".all").prop("checked",false)
      }
      zongjia()
     })
     $(".lla").change(function(){
      zongjia()
     })
     function zongjia(){
      var xuan=$(".lla:checked").parents(".zuida");
      var num=0;
      xuan.each(function(index,rom){
       var xuanzhi=$(rom).find(".zongji").text()*1;
       num+=xuanzhi;
      })
      $(".zongjia").text(num);
     }
    })
</script>