Example for multer upload custom error handling

example-multer-custom-error.js

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

const app = express();

const storage = multer.diskStorage({
    destination: function (req, file, cb) {
        cb(null, 'tmp')
    },
    filename: function (req, file, cb) {
        cb(null, file.fieldname + '-' + Date.now())
    }
})

const upload = multer({
    storage: storage,
    limits: {
        fileSize: 1024 * 1024 * 5
    },
    fileFilter: (req, file, cb) => {
        if (file.mimetype == "image/png" || file.mimetype == "image/jpg" || file.mimetype == "image/jpeg") {
            cb(null, true);
        } else {
            return cb(new Error('Invalid mime type'));
        }
    }
});

const uploadSingleImage = upload.single('image');

app.post('/upload', function (req, res) {

    uploadSingleImage(req, res, function (err) {

        if (err) {
            return res.status(400).send({ message: err.message })
        }

        // Everything went fine.
        const file = req.file;
        res.status(200).send({
            filename: file.filename,
            mimetype: file.mimetype,
            originalname: file.originalname,
            size: file.size,
            fieldname: file.fieldname
        })
    })
})

app.listen(3000, () => {
    console.log("Server is listening on port: 3000");
});

My multer function is in middleware, How to put error in the controller?

My multer function is in middleware, How to put error in the controller?

Just return callback with error in fileFilter:

const upload = multer({
   dest: "uploads",
   fileFilter(req, file, callback) {
      if (encodeURI(file.originalname).length > 30) {
         // You can throw any error or MulterError(code)
         return callback(new CustomHttpError("File name must contain no more 30 symbols", 413));
      }
      callback(null, true);
   },
});

You can read more about error codes and their processing here - https://github.com/expressjs/multer#filefilter

Thanks man, you're a life saver

Hello , why my app is hang when i hit the endpoint twice, if you try on postman, it will hang with "Sending request..." message

This is my code :

R_menu.js

const MW_MULTER = [handlerUploadImage];
router.post("/upload-image", MW_MULTER, C_menu.uploadImage);

MW_menu.js

const handlerUploadImage = (req, res) => {
  console.log("Handler Upload Image middleware reached");

  const h = upload.single("image");
  h(req, res, function (err) {
    if (err) {
      return res.status(400).send({ message: err.message });
    }
  });
};

Hello , why my app is hang when i hit the endpoint twice, if you try on postman, it will hang with "Sending request..." message

This is my code :

R_menu.js

const MW_MULTER = [handlerUploadImage];
router.post("/upload-image", MW_MULTER, C_menu.uploadImage);

MW_menu.js

const handlerUploadImage = (req, res) => {
  console.log("Handler Upload Image middleware reached");

  const h = upload.single("image");
  h(req, res, function (err) {
    if (err) {
      return res.status(400).send({ message: err.message });
    }
  });
};

Every middleware should call next handler or throw error (or smth). Your handlerUploadImage takes 3 parameters: req, res and next. Call next() in your handler, and request will be transferred into C_menu.uploadImage

"Hello @nacza,

I've encountered an issue while uploading '.png' files and it seems you're facing the same problem. Could you please review my code on GitHub (https://github.com/codal-umistri/Multer).

It will help You!