downloadCount

downloadCount.js

const collectionName = 'downloads';

// Create or update the document with the matching fileId
const fileId = '1234';
const downloadCount = 1;
const email = '';

// Options for findOneAndUpdate method
const options = { upsert: true, new: true };

// Query to find the document with the matching fileId
const query = { fileId };

// Update the 'downloadCount' and 'email' fields in the document with the matching fileId, or create a new document if one is not found
const update = { $inc: { downloadCount} };

// Use findOneAndUpdate to save the document
const savedDocument = await db.collection(collectionName).findOneAndUpdate(query, update, options);

console.log(`Document saved: ${savedDocument}`);

updateDownloadCoun()t.js

const MongoClient = require('mongodb').MongoClient;

const uri = 'mongodb+srv://<username>:<password>@<cluster-address>/test?retryWrites=true&w=majority';
const client = new MongoClient(uri, { useNewUrlParser: true, useUnifiedTopology: true });

async function updateDownloadCount(fileId) {
  try {
    await client.connect();

    const database = client.db('test');
    const collection = database.collection('downloadedFiles');

    const filter = { _id: fileId };
    const update = { $inc: { downloadCount: 1 } };
    const options = { upsert: true };

    const result = await collection.findOneAndUpdate(filter, update, options);

    console.log(`Download count updated for file with ID ${fileId}.`);
  } catch (err) {
    console.error(err);
  } finally {
    await client.close();
  }
}

updateDownloadCount('file123');

viewdownloadsroute.js

const express = require('express');
const router = express.Router();
const collectionName = 'downloads';

router.get('/downloads', async (req, res) => {
  try {
    const downloads = await db.collection(collectionName).find({}).toArray();
    return res.send(downloads);
  } catch (err) {
    console.error(err);
    return res.status(500).send({ message: 'Internal server error' });
  }
});

module.exports = router;

You can either try the first solution or the function.
Lemme know how it goes.