问题 Browser-side code let data = new FormData(); data.append('file', file); data.append('userId', userId); axios.post(`${baseUrl}/uploadFile`, data, {headers: {'Content-Type':'multipart/form-data'}}).then((result) => console.log(result)).catch((err) => cb(err)) Server side code app.use((req, res, next) => { res.setHeader('Access-Control-Allow-Origin', '*'); res.setHeader('Access-Control-Allow-Methods', 'GET, POST, DELETE, PUT, PATCH, OPTIONS'); res.setHeader('Access-Control-Allow-Headers',