app.js

const express = require('express')
const app = express()
const uploadRouter = require('./upload.route')

app.use(uploadRouter)

app.listen(3000, () => {
console.log('Server is running on port 3000')
})

cloudinary.js

const cloudinary = require("cloudinary");

cloudinary.config({
    cloud_name: process.env.CLOUD_NAME,
    api_key: process.env.API_KEY,
    api_secret: process.env.API_SECRET,
});

module.exports = async (file) => {
    return await cloudinary.uploader.upload(file.path);
}

multer.js

const path = require("path");
const multer = require("multer");

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

function checkFileType(file, cb) {
    const filetypes = /jpeg|jpg|png|gif/;

    const extname = filetypes.test(path.extname(file.originalname).toLowerCase());
    const mimetype = filetypes.test(file.mimetype);

    if (extname && mimetype) {
        return cb(null, true);
    } else {
        cb("Error: Images only!");
    }
}

module.exports = multer({
    storage: storage,
    fileFilter: function (req, file, cb) {
        checkFileType(file, cb);
    },
});

upload.controller.js

module.exports = async function changeProfilePicture(req, res) {
  const { id } = req.params
  const profile_picture = req.body.profile_picture[0]
  const existingUser = await User.find({_id: id})
  
  if(!existingUser) {
//tell them user does not wxist
  }
  
  const updatedUser = await User.update(id, {
    profile_picture: profile_picture
  }
     
//return response to the frontend after                        
}

upload.middleware.js

const uploadToCloudinary = require( './cloudinary')

module.exports = (fieldToAccessUploadedFiles) => async (req, res, next) => {
    const uploads = []
    if (req.files && req.files.length > 0) {
        for (const file of req.files) {
            const result = await uploadToCloudinary(file)
            console.log(result);
            uploads.push({ ...file, ...result })
        }
    }
    req.body[fieldToAccessUploadedFiles] = uploads
    console.log(`File(s) uploaded successfully. Field to access uploaded file(s): req.body.${fieldToAccessUploadedFiles}`);
    console.log('Uploaded File(s):', req.body[fieldToAccessUploadedFiles]);
    
    next()
}

upload.route.js

const uploadFiles = require('./upload.middleware')
const { upload } = require('./multer')
const changeProfilePicture = require('upload.controller')

const uploadRouter = Router()

uploadRouter.post('/users/:id/upload_profile_picture', [upload.array('profile_picture', 1), uploadFiles('profile_picture')], changeProfilePicture)

module.exports = uploadRouter