ajinkya-mhetre-mern/backend/src/middleware/upload.js

A MERN starter with frontend and backend folders

// ===== src/middleware/upload.js =====
const multer = require('multer');
const path = require('path');

const storage = multer.diskStorage({
  destination: (req, file, cb) => {
    cb(null, 'uploads/');
  },
  filename: (req, file, cb) => {
    cb(null, `${Date.now()}-${Math.round(Math.random() * 1E9)}${path.extname(file.originalname)}`);
  }
});

const fileFilter = (req, file, cb) => {
  if (file.mimetype.startsWith('image/')) {
    cb(null, true);
  } else {
    cb(new Error('Only image files are allowed!'), false);
  }
};

const upload = multer({
  storage,
  fileFilter,
  limits: { fileSize: 5 * 1024 * 1024 } // 5MB limit
});

module.exports = upload;