adding all the functionality to package multer for image uploading

multer-config.js

const multer = require("multer")
const express = require("express")
const app = express()

const storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, __dirname + "/uploads")
  },
  filename: function (req, file, cb) {
    const firstname = file.originalname.split(".")[0]
    const lastname = file.originalname.split(".")[1]
    const newname = firstname + `anything-here` + lastname
    
    cb(null, newname)
  }
})

const upload = multer({
  storage,
  limits: {
    fileSize: 1000000 // in kbs
  },
  fileFilter(req, file, cb) {
    if (!file.originalname.match(/\.(doc|docx)$/)) {
      return cb(new Error("Please upload a valid word document"))
    }
    
    cb(undefined, true)
  }
})

app.post("/users/upload", upload.single("upload"), (req, res) => {
  res.send()
}, (error, req, res, next) => {
  res.status(400).send({ error: error.message })
})

app.listen(3000)