如何检查表单是否不包含任何数据

<form id="myForm">
  <input type="text" name="username" />
  <input type="password" name="password" />
  <select name="country">
    <option value="">Select Country</option>
    <option value="usa">USA</option>
    <option value="canada">Canada</option>
  </select>
  <input type="radio" name="gender" value="male" /> Male
  <input type="radio" name="gender" value="female" /> Female
  <button type="submit">Submit</button>
</form>

function isFormEmpty(formId) {
  const form = document.getElementById(formId);
  const elements = form.elements;

  for (let i = 0; i < elements.length; i++) {
    const element = elements[i];
    const type = element.type;
    const tagName = element.tagName.toLowerCase();

    if (type === 'text' || type === 'password') {
      if (element.value.trim() !== '') return false;
    } else if (tagName === 'select') {
      if (element.value !== '') return false;
    } else if (type === 'radio') {
      if (document.querySelector(`input[name="${element.name}"]:checked`)) return false;
    }
    // 可以继续添加其他类型的表单元素检查
  }

  return true; // 表单为空
}

// 使用示例
document.getElementById('myForm').addEventListener('submit', function(event) {
  if (isFormEmpty('myForm')) {
    alert('表单不能为空');
    event.preventDefault(); // 阻止表单提交
  }
});