我有一个带有表单的html页面。当我用form.submit（）提交数据时，一切正常。当我尝试使用fetch时，服务器输出的信息为未定义
委托单位：

<form id="form" action="/submit-reservation" method="POST"> 
      <label for="name">Surname:</label><br>
      <input type="text" name="name"><br>
      <label for="address">Address:</label><br>
      <input type="text" name="address"><br>
      <label for="town">Town/City:</label><br>
      <input type="text" name="town"><br>
      <label for="email">Email address:</label><br>
      <input type="email" name="email"><br><br>
      <center>
        <a onclick="form.submit();" class="button">Submit</a>
        <a onclick="fetch('/submit-reservation', { method: 'POST', body: new FormData(form) });" class="button">Submit</a>
      </center>
</form>

伺服器：

app.post("/submit-reservation", (req, res) => {
  console.log(req.body);
  res.end();
});

form.submit（）函数返回：{姓名：'，地址：“”，城镇：“ASDF”，电子邮件：“”}
提取返回：{}
我检查了客户端上的表单数据是否正确，结果正确。
编辑：这是我的代码后的解决方案

<form id="form" action="/submit-reservation" method="POST"> 
      <label for="name">Surname:</label><br>
      <input type="text" name="name"><br>
      <label for="address">Address:</label><br>
      <input type="text" name="address"><br>
      <label for="town">Town/City:</label><br>
      <input type="text" name="town"><br>
      <label for="email">Email address:</label><br>
      <input type="email" name="email"><br><br>
      <center>
        <a onclick="fetch('/submit-reservation', { method: 'POST', body: new URLSearchParams(new FormData(form)) });" class="button">Submit</a>
      </center>
</form>