React-native获取上传具有formdata的文件和消息，服务器未获取文件，但仍获取消息和id

import RNFetchBlob from 'react-native-fetch-blob';

// 创建FormData对象
const formData = new FormData();

// 添加文件到FormData
formData.append('file', {
  uri: 'file://path/to/file',
  name: 'filename',
  type: 'image/jpeg',
});

// 添加消息到FormData
formData.append('message', 'Hello, server!');
formData.append('id', '12345');

// 发送网络请求
RNFetchBlob.fetch('POST', 'https://example.com/upload', {
  'Content-Type': 'multipart/form-data',
}, formData)
  .then((response) => {
    // 处理响应
  })
  .catch((error) => {
    // 处理错误
  });

const express = require('express');
const multer = require('multer');

const app = express();
const upload = multer({ dest: 'uploads/' });

// 处理文件上传和消息获取的路由
app.post('/upload', upload.single('file'), (req, res) => {
  // 获取上传的文件
  const file = req.file;

  // 获取消息和id
  const message = req.body.message;
  const id = req.body.id;

  // 处理文件和消息
  // ...

  res.send('Upload successful');
});

// 启动服务器
app.listen(3000, () => {
  console.log('Server started on port 3000');
});