Xtykutl

I came acorss snippet to write file to gridfs, but I am unable to find write way to update string to Gridfs.

the below snippet will update using path, but what about direct string buffer?

var metadata = {

    "path": path

};

var writestream = gfs.createWriteStream({

    filename: name,

    mode: 'w',

    content_type: type,

    metadata: metadata

});

fs.createReadStream(path).pipe(writestream);

//    var buf = new Buffer("hello");

writestream.on('close', function (file) {

    console.log("Gridfs created");

});

I was faced with the same problem. I just simply deleted the file using gfs.remove and then added the updated file to GridFS.

Also FYI. I used async.series to finish the delete operation first and then write the updated file to GridFS.

Hope this helps!

Even though it's been a while. I had this problem and solved it creating a stream from the string instead of a file.
Like this:

  var writestream = gfs.createWriteStream({

      filename: fileName

  });



  // Create stream with buffer to pipe to writestream

  var s = new stream.Readable();

  s.push(pic);

  s.push(null); // Push null to end stream

  s.pipe(writestream);



  writestream.on('close', function (file) {

    // Do anything with the file

    cb(null, file.filename);

  }).on('error', cb);

Got the stream idea from here

This page comes up first when searching for how to store a string data in Mongo GridFS using NodeJS. Since most of the answers here and elsewhere are based on deprecated API, I decided to post a code based on a more recent GridFSBucket. The code has an additional provision to overwrite existing files. If you don't need that - you can replace openUploadStreamWithId with openUploadStream which creates duplicates.

var mongo = require('mongodb');

var stream = require('stream');

var MongoClient = mongo.MongoClient;



function getFileSystemItem(dbo, filename) {

  var buf = new Buffer('');

  return new Promise(function(resolve, reject) {

    var bucket = new mongo.GridFSBucket(dbo);

    var readstream = bucket.openDownloadStream(filename);

    readstream.on('data', (chunk) => {

      buf = Buffer.concat([buf, chunk]);

    });

    readstream.on('error', (err) => {

        reject(err);

    });

    readstream.on('end', () => {

        var res = buf.toString();

        buf = null; // Clean up memory

        readstream.destroy();

        resolve(res);

    });

  });

}



function putFileSystemItem(dbo, filename, data) {

  var putItemHelper = function(bucket, resolve, reject) {

    var writeStream = bucket.openUploadStreamWithId(filename, filename);

    var s = new stream.Readable();

    s.push(data);

    s.push(null); // Push null to end stream

    s.pipe(writeStream);

    writeStream.on('finish', resolve);

    writeStream.on('error', reject);

  };

  return new Promise(function(resolve, reject) {

    var bucket = new mongo.GridFSBucket(dbo);

    bucket.find({_id: filename}).count(function(err, count) {

      if (err) return reject(err);

      if (count > 0) {

          bucket.delete(filename, function() {

          putItemHelper(bucket, resolve, reject);

        }, reject)

      } else {

        putItemHelper(bucket, resolve, reject);

      }

    }, reject);

  });

}



function test() {

  var MongoUrl = 'mongodb://localhost:27017';

  var dbName = 'test';

  MongoClient.connect(MongoUrl, function(err, db) {

    if (err) throw err;

    var dbo = db.db(DbName);

    putFileSystemItem(dbo, 'test', 'this is a test')

    .then(function(a) {

      console.log('Wrote a gridFS file with metadata:', a);

      return getFileSystemItem(dbo, 'test')

    })

    .then(function(a) {

      console.log('Got data back from a gridFS file:', a);

      db.close();

    })

    .catch(function(e) {

      console.log(e);

      db.close();

    })

  });

}

test();

Credit: This is assembled from a dozen of other StackOverflow pages and MongoDB API help.