app_4.js

const upload = multer({
	storage: multer.diskstorage({
		destination: "/upload/images",  // Storage location
		filename: (req, res, (cb) => {
			cb(null, Date.now() + path.extname(file.originalname)) // return a unique file name for every file				
		})
	}),
	
	limits: {fileSize: 20000000,   // This limits file size to 2 million bytes(2mb)
		 
	fileFilter: (req, file, cb) => {
		const validFileTypes = /jpg|jpeg|png/ // Create regex to match jpg and png
		
		// Do the regex match to check if file extenxion match
		const extname = validFileTypes.test(path.extname(file.originalname).toLowerCase())
		
		if(extname === true){
			// Return true and file is saved
			 return cb(null, true)
		}else{
			// Return error message if file extension does not match
			 cb("Error: Images Only!")
			}
		}
})