how to download a file saved in gridFS using nodeJS

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);
        }
    });