how to download a file saved in gridFS using nodeJS - node.js

Question

I need to download a resume from GridFS, below is the code ive written to do it, but this seems to not give me a physical file for download, this is used to reading the contents. How can i download the file?
exports.getFileById = function(req, res){
var conn = mongoose.connection;
var gfs = Grid(conn.db, mongoose.mongo);
var id = req.params.ID;
gfs.exist({_id: id,root: 'resume'}, function (err, found) {
if (err) return handleError(err);
if (!found)
return res.send('Error on the database looking for the file.');
gfs.createReadStream({_id: id,root: 'resume'}).pipe(res);
});
};

Answer 1

Hope this helps!
exports.downloadResume = function(req, res){
var conn = mongoose.connection;
var gfs = Grid(conn.db, mongoose.mongo);
gfs.findOne({ _id: <resumeId>, root: <collectionName> }, function (err, file) {
if (err) {
return res.status(400).send(err);
}
else if (!file) {
return res.status(404).send('Error on the database looking for the file.');
}
res.set('Content-Type', file.contentType);
res.set('Content-Disposition', 'attachment; filename="' + file.filename + '"');
var readstream = gfs.createReadStream({
_id: <resumeId>,
root: '<collectionName>'
});
readstream.on("error", function(err) {
res.end();
});
readstream.pipe(res);
});
};

Answer 2

I took hints from accepted answer. But I had to jump through some hoops to get it working hope this helps.
const mongodb = require('mongodb');
const mongoose = require('mongoose');
const Grid = require('gridfs-stream');
eval(`Grid.prototype.findOne = ${Grid.prototype.findOne.toString().replace('nextObject', 'next')}`);
const mongoURI = config.mongoURI;
const connection = mongoose.createConnection(mongoURI);
app.get('/download', async (req, res) => {
var id = "<file_id_xyz>";
gfs = Grid(connection.db, mongoose.mongo);
gfs.collection("<name_of_collection>").findOne({ "_id": mongodb.ObjectId(id) }, (err, file) => {
if (err) {
// report the error
console.log(err);
} else {
// detect the content type and set the appropriate response headers.
let mimeType = file.contentType;
if (!mimeType) {
mimeType = mime.lookup(file.filename);
}
res.set({
'Content-Type': mimeType,
'Content-Disposition': 'attachment; filename=' + file.filename
});
const readStream = gfs.createReadStream({
_id: id
});
readStream.on('error', err => {
// report stream error
console.log(err);
});
// the response will be the file itself.
readStream.pipe(res);
}
});