MulterS3 - Control flow to check req object - node.js

Question

I'm trying to use Multer-S3, and it works like a charm to upload images.
My challenge is that before running the Multer-S3 middleware, I want to have some kind of control flow, where it's possible to check if the req.body contains numbers for some fields, if the file is of a specific type etc before the Multer-S3 middleware runs.
As I'm using form-data, I need to use multer or similar to get access to the req.body and the req.file, but if I use another middleware with multer, it no longer works.
Anyone got ideas how to do this?
Below sample code to try to explain:
const express = require('express'); //"^4.13.4"
const aws = require('aws-sdk'); //"^2.2.41"
const bodyParser = require('body-parser');
const multer = require('multer'); // "^1.3.0"
const multerS3 = require('multer-s3'); //"^2.7.0"
aws.config.update({
secretAccessKey: 'YOUR_ACCESS_SECRET_KEY',
accessKeyId: 'YOUR_ACCESS_KEY_ID',
region: 'us-east-1'
});
const app = express();
const s3 = new aws.S3();
app.use(bodyParser.json());
const upload = multer({
storage: multerS3({
s3: s3,
acl: 'public-read',
bucket: 'YOUR_BUCKET_NAME',
key: function (req, file, cb) {
console.log(file);
cb(null, file.originalname); //use Date.now() for unique file keys
}
})
});
//This is where I would like to add some controll flow to check the req.body and req.file
// before the middleware upload is used.
//When using another multer middleware before to get access to the req body and file,
//it seems I can't use the upload middleware to upload..
app.post('/upload', upload.single("file"), (req, res, next) => {
res.send("Uploaded!");
});
app.listen(3000, () => {
console.log('Example app listening on port 3000!');
});
Anyone able to help?
Best regards,
Oscar

Answer 1

This works for me:
let formData = new FormData()
formData.append('param', this.data)
formData.append('dataForFile', this.$refs.file.files[0])
this.$axios.post(`/file/upload`, formData)
.then(data => {
...
})
It's important to remember that you place the file data last in the formData list.