使用键盘在提交按钮上按enter键且输入字段为空时，自定义web辅助功能错误消息

<form>
  <input type="text" id="inputField" aria-describedby="errorField">
  <button type="submit" id="submitButton">Submit</button>
  <div id="errorField" role="alert" aria-live="assertive"></div>
</form>

<script>
  const inputField = document.getElementById('inputField');
  const submitButton = document.getElementById('submitButton');
  const errorField = document.getElementById('errorField');

  submitButton.addEventListener('keydown', function(event) {
    if (event.key === 'Enter') {
      if (inputField.value.trim() === '') {
        event.preventDefault(); // 阻止表单提交
        showError('请输入有效的内容');
      }
    }
  });

  function showError(message) {
    errorField.textContent = message;
    errorField.style.display = 'block';
  }
</script>