cats.js

const router = require('express').Router();
const upload = require('./upload')('./cats');

router.post('/', upload.array('photos', 10), (req, res) => {
 // handle logic
 res.send('ok');
});

module.exports = router;

dogs.js

const router = require('express').Router();
const upload = require('./upload')('./dogs');

router.post('/', upload.array('photos', 10), (req, res) => {
 // handle logic
 res.send('ok');
});

module.exports = router;

upload.js

const multer = require('multer');

function customStore(dirPath) {
  return multer.diskStorage({
    destination: (req, file, cb) => {
      cb(null, dirPath);
    },
    filename: (req, file, cb) => {
      const fname = `${Date.now()}-${encodeURIComponent(file.originalname)}`;
      cb(null, fname);
    },
  });
}

const upload = (dirPath) => multer({
  storage: customStore(dirPath),
});

module.exports = upload;