Expressjs Multer Error Handling with Array - express

Question

I am using multer's array method as a middleware for my post route and I'm trying to figure out how I can send the error callback from the fileFilter function in the multer options setup as a flash message when the group of files that a user is uploading contains at least one file with the wrong format. My current fileFilter setup achieves this, but instead of sending the user to a blank page with the File Selected is not supported message, I was looking for a way to communicate that to the route using multer as middleware.
Here is my multer setup:
var upload = multer({
storage: multerS3({
s3: s3,
bucket: options.Bucket,
contentType: multerS3.AUTO_CONTENT_TYPE,
acl: options.ACL,
key: function(req, file, cb){
var fileNameFormatted = file.originalname.replace(/\s+/g, '-').toLowerCase();
cb(null, req.user.organizationId + '/' + uploadDate + '/' + fileNameFormatted);
}
}),
fileFilter: function(req, file, cb){
if(!file.originalname.match(/\.(jpg|jpeg|png|gif|csv|xls|xlsb|xlsm|xlsx)$/)){
return cb('File Selected is not supported');
}
cb(null, true);
}
});
Here is my route with upload.array('fileUpload', 5) fileUpload is the name of my file input field and 5 is the multer file length limiting feature.
.post(upload.array('fileUpload', 5), function(req, res) {
//Configure Uploaded S3 File Path strings based on environment for use in DB
var uploadedFiles = req.files;
var s3FilePath = [];
for (var prop in uploadedFiles) {
console.log(uploadedFiles[prop].key);
if (app.get('env') === 'production' || app.get('env') === 'staging') {
s3FilePath = 'https://files.test-site.com/' + uploadedFiles[prop].key;
} else {
s3FilePath.push(uploadedFiles[prop].location);
}
}
models.Blog.update({
blogId: req.body.blogId,
blogDate: req.body.blogDate,
}, {
where: {
userId: req.user.userId,
blogId: req.body.blogId
}
}).then(function(blog) {
console.log('This is the blog ' + blog);
var files = _.map(s3FilePath, function(file) {
console.log(file);
return {
fileName: file,
blogId: req.body.blogId
};
});
return models.BlogFile.bulkCreate(files);
}).then(function() {
res.redirect('/app');
}).catch(function(err) {
res.send(err);
console.log('File Post Error ' + err);
});
});