async function uploadFiles(files, textData) {
  const formData = new FormData();

  // Append text data (e.g., userId, description)
  for (const key in textData) {
    formData.append(key, textData[key]);
  }

  // Append files (can be multiple)
  for (let i = 0; i < files.length; i++) {
    formData.append('files', files[i], files[i].name); // 'files' is the field name on the server
  }

  try {
    const response = await fetch('https://api.example.com/upload', {
      method: 'POST',
      body: formData, // fetch API automatically sets 'Content-Type': 'multipart/form-data'
      // headers: {
      //   'Authorization': 'Bearer YOUR_AUTH_TOKEN' // Add authorization if needed
      // }
    });

    if (!response.ok) {
      const errorText = await response.text();
      throw new Error(`Upload failed with status ${response.status}: ${errorText}`);
    }

    const result = await response.json();
    console.log('Upload successful:', result);
    return result;
  } catch (error) {
    console.error('Error during file upload:', error);
    throw error;
  }
}

// Usage example (requires an HTML input type="file" element):
document.addEventListener('DOMContentLoaded', () => {
  const fileInput = document.getElementById('file-upload-input');
  const uploadButton = document.getElementById('upload-button');

  if (uploadButton && fileInput) {
    uploadButton.addEventListener('click', async () => {
      const filesToUpload = fileInput.files;
      if (filesToUpload.length === 0) {
        alert('Please select files to upload.');
        return;
      }

      const additionalData = {
        userId: 'user123',
        description: 'My awesome files'
      };

      try {
        await uploadFiles(filesToUpload, additionalData);
        alert('Files uploaded successfully!');
      } catch (error) {
        alert(`File upload failed: ${error.message}`);
      }
    });
  }
});