My code works but I don’t think it is good. How to improve it?

Is there a way to beautify my code? It works but there repeated blocks and I am not sure that I’m using some functions in the right way.
I’m not new to javascript but I want to improve it and get rid of Bad Coding Habits.

Below is my code snippet that I’m using on the server to upload product images to cloud storage using multer and sharp.

const EasyYandexS3 = require('easy-yandex-s3')
const multer = require('multer')
const sharp = require('sharp')
const slug = require('slug')

const s3 = new EasyYandexS3({
  auth: {
    accessKeyId: process.env.KEY_ID,
    secretAccessKey: process.env.SECRET_KEY,
  },
  Bucket: process.env.BACKET, // Название бакета
  debug: false, // Дебаг в консоли
})

const storage = multer.memoryStorage()
const fileFilter = (req, file, cb) => {
  if (
    file.mimetype === 'image/jpeg' ||
    file.mimetype === 'image/jpg' ||
    file.mimetype === 'image/png'
  ) {
    cb(null, true)
  } else {
    cb(null, false)
  }
}

const upload = multer({
  storage,
  fileFilter,
  limits: {
    fileSize: 1024 * 1024 * 5, // ограничение до 5 мб
  },
})

const uploadFields = upload.fields([
  { name: 'cover', maxCount: 1 },
  { name: 'media', maxCount: 4 },
])

const uploadImages = (req, res, next) => {
  uploadFields(req, res, (err) => {
    if (err instanceof multer.MulterError) {
      if (err.code === 'LIMIT_UNEXPECTED_FILE') {
        return res.send('Превышено количество файлов.')
      }
    } else if (err) {
      return res.send(err)
    }
    next()
  })
}
const resizeImages = async (req, res, next) => {
  // Функция загрузки фотографий в бакет
  async function transform(size, file, filename, type) {
    const folder = slug(req.body.title)
    const resizedImgFilename = `${filename}-${size}`
    const resizedImgBuffer = await sharp(file.buffer)
      .resize(size)
      .toFormat('jpeg')
      .jpeg({ quality: 90 })
      .toBuffer()
    const upload = await s3.Upload(
      {
        buffer: resizedImgBuffer,
        name: resizedImgFilename,
      },
      `/products/${folder}/`
    )
    if (size === 800) {
      type.push(upload.Location.slice(0, -4))
    }
  }

  // Проверяем какие файл загружены
  if (req.files.media === undefined && req.files.cover === undefined) {
    return next()
  } else if (req.files.media === undefined) {
    await Promise.all(
      req.files.cover.map(async (file) => {
        const filename = Date.now() + Math.round(Math.random() * 1e2) + 'c'
        const type = req.body.cover
        await transform(800, file, filename, type)
        await transform(400, file, filename, type)
        await transform(250, file, filename, type)
      })
    )
  } else if (req.files.cover === undefined) {
    await Promise.all(
      req.files.media.map(async (file) => {
        const filename = Date.now() + Math.round(Math.random() * 1e2) + 'm'
        const type = req.body.media
        await transform(800, file, filename, type)
        await transform(400, file, filename, type)
        await transform(250, file, filename, type)
      })
    )
  } else {
    await Promise.all(
      req.files.media.map(async (file) => {
        const filename = Date.now() + Math.round(Math.random() * 1e2) + 'm'
        const type = req.body.media
        await transform(800, file, filename, type)
        await transform(400, file, filename, type)
        await transform(250, file, filename, type)
      })
    )
    await Promise.all(
      req.files.cover.map(async (file) => {
        const filename = Date.now() + Math.round(Math.random() * 1e2) + 'c'
        const type = req.body.cover
        await transform(800, file, filename, type)
        await transform(400, file, filename, type)
        await transform(250, file, filename, type)
      })
    )
  }
  next()
}

module.exports = {
  uploadImages,
  resizeImages,
}