fileUpload.js

const multer = require('multer');
const path = require('path');
const config = require('../config/index');

const pathToUploads = config.uploadDestination;

const limits = {
    fileSize: 5242880
}

const storage = multer.diskStorage({
    destination: function (req, file, cb) {
        cb(null,  pathToUploads);
    },
    filename: function (req, file, cb) {
        cb(null, `${ file.fieldname }-${ Date.now() }${ path.extname(file.originalname) }`);
    }
});

/** todo: file filter to accept only images
 * */
function fileFilter(req, file, cb) {
    if (!file.originalname.match(/\.(jpg|jpeg|png|gif)$/)) {
        return cb(new Error('Only image files are allowed!'));
    }
    cb(null, true);

}

const upload = multer({ storage, limits });

module.exports = upload;

this is how multer accept any file type but this is for single file upload.