Node.js中MulterError: Unexpected field问题排查求助

我基于Express、Multer和MongoDB编写了图片上传至数据库并在网站展示的后端代码：

var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://127.0.0.1:27017/"; 
var express = require('express');
var router = express.Router();
 const multer = require('multer');
 const dbName = "cars"; 
 const collectionName = "car-name"; 


const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    cb(null, 'C:/Users/tahaa/OneDrive/Desktop/yourcar edit/front-end/src/cars/');
  },
  filename: (req, file, cb) => {
    cb(null, Date.now() + '-' + file.originalname);
  }
});

const upload = multer({ storage: storage });

router.post('/', upload.single('file'), (req, res) => {
  const carImg = req.file.path;
  const carName = req.body.carName;
  const carType = req.body.carType;
  const carYear = req.body.carYear;
  const carColor = req.body.carColor;
  const carDescription = req.body.carDescription;
  const carPrice = req.body.carPrice;
  const carKm = req.body.carKm;

  MongoClient.connect(url, { useUnifiedTopology: true })
    .then((client) => {
      const db = client.db(dbName);
      const collection = db.collection(collectionName);
      const myobj = {
        carImg: carImg,
        carName: carName,
        carType: carType,
        carYear: carYear,
        carColor: carColor,
        carDescription: carDescription,
        carPrice: carPrice,
        carKm: carKm
      };

      return collection.insertOne(myobj);
    })
    .then(() => {
      res.json({ message: 'File uploaded successfully!' });
      console.log('File uploaded successfully!');
    })
    .catch((err) => {
      console.error('Failed to save image path in MongoDB', err);
      res.status(500).json({ message: 'Failed to save image path in MongoDB' });
    });
});

使用Postman测试接口时，出现如下错误：

MulterError: Unexpected field
    at wrappedFileFilter (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\multer\\index.js:40:19)
    at Multipart.<anonymous> (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\multer\\lib\\make-middleware.js:107:7)
    at Multipart.emit (node:events:513:28)
    at HeaderParser.cb (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\busboy\\lib\\types\\multipart.js:358:14)
    at HeaderParser.push (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\busboy\\lib\\types\\multipart.js:162:20)
    at SBMH.ssCb [as _cb] (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\busboy\\lib\\types\\multipart.js:394:37)
    at feed (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\streamsearch\\lib\\sbmh.js:200:10)
    at SBMH.push (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\streamsearch\\lib\\sbmh.js:104:16)
    at Multipart._write (C:\\Users\\tahaa\\OneDrive\\Desktop\\node_modules\\busboy\\lib\\types\\multipart.js:567:19)
    at writeOrBuffer (node:internal/streams/writable:392:12)

该错误源于Multer中间件指定的字段名与客户端请求的字段名不匹配，按以下步骤排查：

• 确认客户端请求的文件字段名与代码中upload.single('file')里的'file'完全一致
• 确保请求中包含carName、carType、carYear等所有必要字段
• 检查文件存储目录是否存在，且服务器拥有该目录的写入权限

若排查后问题仍未解决，可寻求进一步技术协助。

内容的提问来源于stack exchange，提问作者Taha ik