飞镖未获得输入值

我有一个Dart脚本，该脚本从两个<input>元素获取值并比较它们以检查它们是否相等。但是出于某种奇怪的原因，其中一个<input>元素的值始终是""（即使我在内部引入了文本）两个输入的代码都是相同的，并且对于其中一个输入，它的工作原理是完美的。

这些是输入：

Contraseña:<input maxlength="30" name="psswd" type="password"><br>
Confirmar contraseña:<input maxlength="30" name="psswd-confirm" type="password"><br>

这是Dart代码，用于检查它们的值是否相等（在用户单击按钮时调用）

InputElement passwordInput = querySelector('[name="psswd"]');
InputElement psswdConfirmInput = querySelector('[name="psswd-confirm"]');
if (passwordInput.value != psswdConfirmInput.value) {
  showBlock(querySelector("#signup-psswd-error1"));
  return;
}

该showBlock()功能仅更改元素的样式即可display: block，而我认为没有问题。

编辑整个表单的代码如下：

<form name="signup" id="form-signup" action="http://localhost:8080" method="post">
      <span id="signup-email-error1">Esta dirección de correo electrónico ya ha sido registrada.</span>
      <span id="signup-email-error2">Las dos direcciones de correo electrónico no coinciden.</span>
      <span id="signup-psswd-error1">Las dos contraseñas no coinciden.</span>
      <span id="signup-empty-error1">Debes completar todos los campos.</span>
      Correo electrónico:<input maxlength="30" name="email" type="email" value=""><br>
      Confirmar correo:<input maxlength="30" name="confirm-email" type="email" value=""><br>
      Contraseña:<input maxlength="30" name="psswd" type="password"><br>
      Confirmar contraseña:<input maxlength="30" name="psswd-confirm" type="password"><br>
      Nombre y apellidos:<input maxlength="30" name="name" type="text" value=""><br>
      <button id="signup-submit">Crear cuenta</button>
  </form>

该<span>元素是默认隐藏，只显示在错误的错误消息。

编辑HTML已经通过，没有任何错误，也没有警告w3c验证程序进行验证，因此可能不存在该错误。与错误相关的dart事件侦听器功能的代码如下：

signupSubmit.onClick.listen((e) {
 e.preventDefault();
 for (int i = 0; i < signupForm.children.length; i++) { //AUTOMATIC HIDING
   if (signupForm.children[i] is SpanElement) {
     hide(signupForm.children[i]);
   }
 }
 for (int i = 0; i < signupForm.children.length; i++) { //CHECK FOR EMPTY FIELDS
   Element element = signupForm.children[i];
   if (element is InputElement) {
     if (element.value == "") {
       showBlock(querySelector("#signup-empty-error1"));
       return;
     }
   }
 }
 InputElement emailInput = querySelector('[name="email"]');
 InputElement emailConfirmInput = querySelector('[name="confirm-email"]');
 if (emailInput.value != emailConfirmInput.value) {
   showBlock(querySelector("#signup-email-error2"));
   return;
 }
 InputElement passwordInput = querySelector('[name="psswd"]');
 InputElement psswdConfirmInput = querySelector('[name="psswd-confirm"]');
 hide(passwordInput);
 hide(psswdConfirmInput);
 print('passwordInput: ${passwordInput.value}');
 print('confirm: ${psswdConfirmInput.value}');
 if (passwordInput.value != psswdConfirmInput.value) {
   showBlock(querySelector("#signup-psswd-error1"));
   print('psswd different');
   return;
 }
 var req = new HttpRequest();

 req.onReadyStateChange.listen((e) {
   if (req.readyState == HttpRequest.DONE) {
     print(req.responseText);
     if (req.responseText == "regComplete") {
       hide(overlay);
       Element newel1 = new HeadingElement.h1();
       newel1.text = "¡Gracias por registrarte!";
       Element newel2 = new HeadingElement.h2();
       newel2.text = "Se ha enviado un correo electrónico a la dirección proporcionada.";
       Element newel3 = new HeadingElement.h2();
       newel3.text = "Haz click en el enlace recibido para verificar la dirección y confirmar el registro.";
       Element newel4 = new HeadingElement.h4();
       newel4.text = "Del equipo de CampL con ♡";
       querySelector("#welcome")
       ..children.clear()
       ..children.add(newel1)
       ..children.add(newel2)
       ..children.add(newel3)
       ..children.add(newel4);
     } else if (req.responseText == "mailTaken") {
       showBlock(querySelector("#signup-email-error1"));
     }
   }
 });

 req.open('POST', signupForm.action);
 req.send(JSON.encode(serializeForm(signupForm)));
 print('Data submitted!');
 });