Express router with middleware error handling - express

Question

I have a question about error handling with middleware, specifically multer. I have this route:
router.post('/', saveFile, (req, res, next) => {
//rest of code
})
Then I have saveFile middleware:
const multer = require('multer')
const storage = multer.diskStorage({
destination: (req, res, cb) => {
cb(null, './uploads/')
},
filename: (req, res, cb) => {
cb(null, new Date().getTime() + '.jpg')
}
})
const fileFilter = (req, file, cb) => {
if (file.mimetype === 'image/jpeg') cb(null, true)
cb(null, false)
}
const upload = multer({
storage: storage,
limits: {
fileSize: 1024 * 1024 * 3 // up to 3 megabytes
},
fileFilter: fileFilter
})
const saveFile = upload.single('file')
module.exports.saveFile = saveAudio
The issue I have is that when I upload a file with a field name other than file, I get an error MulterError: Unexpected field. I want to catch this error somehow. But I don't even know where to do that. How do I do that?

Answer 1

The answer was pretty simple, yet nobody answered.
in the app.js where express is setup, you can make a middleware for handling errors
app.use((error, req, res, next) => errorHandlers(error, req, res, next))
And put it at last.
and then ErrorHandlers.js:
module.exports = function(error, req, res, next) {
if (error.name === 'MulterError') {
// handle error here
} else {
next()
}
}