Error handling when uploading file using multer with expressjs

Question

I am using multer to save the file on server developed through express & nodejs.

I am usign following code.

var express = require('express'),
    multer  = require('multer')

var app = express()

app.get('/', function(req, res){
  res.send('hello world');
});

app.post('/upload',[ multer({ dest: './uploads/'}), function(req, res){

    res.status(204).end()
}]);

app.listen(3000);

Multer saves the file for me in the specified destination folder.

All this is working fine but I have following questions:

1. If the file saving fails for various reasons, it looks like my route will always return status 204.
2. I am not sure if status 204 is retured after file is saved or while the file is getting saved asynchronously, status 204 is returned.

Answer 1

This is how to write multer middleware that handle upload and errors

const multer = require("multer");

function uploadFile(req, res, next) {
    const upload = multer().single('yourFileNameHere');

    upload(req, res, function (err) {
        if (err instanceof multer.MulterError) {
            // A Multer error occurred when uploading.
        } else if (err) {
            // An unknown error occurred when uploading.
        }
        // Everything went fine. 
        next()
    })
}