如何将HTML小部件的值从HTML表单传递到eXist-db中的Xquery？

<form id="myForm">
  <input type="text" name="name" placeholder="姓名">
  <input type="email" name="email" placeholder="邮箱">
  <input type="submit" value="提交">
</form>

document.getElementById("myForm").addEventListener("submit", function(event) {
  event.preventDefault(); // 阻止表单默认提交行为

  // 获取HTML小部件的值
  var name = document.getElementsByName("name")[0].value;
  var email = document.getElementsByName("email")[0].value;

  // 构建eXist-db的XQuery查询
  var xquery = `
    xquery version "3.1";
    declare variable $name external;
    declare variable $email external;
    
    let $data := <data>
                   <name>{$name}</name>
                   <email>{$email}</email>
                 </data>
    return $data
  `;

  // 发送XQuery查询请求到eXist-db
  // 这里使用的是示例链接，实际情况下需要替换为实际的eXist-db链接
  var existDbUrl = "https://example.com/exist/rest/db";
  var xhr = new XMLHttpRequest();
  xhr.open("POST", existDbUrl);
  xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
  xhr.send("query=" + encodeURIComponent(xquery) + "&name=" + encodeURIComponent(name) + "&email=" + encodeURIComponent(email));

  xhr.onreadystatechange = function() {
    if (xhr.readyState === 4 && xhr.status === 200) {
      var response = xhr.responseText;
      // 处理eXist-db返回的结果
      console.log(response);
    }
  };
});