Read file with node.js, mongoose, gridfs-stream

The example code on GitHub was a little bit misleading; I initially received the same error message you did. In my case, it was due to the fact that I was attempting to read the file before the write stream had finished. I resolved this by doing the read inside the event handler for "close":

var fs = require("fs"),    mongo = require("mongodb"),    Grid = require("gridfs-stream"),    gridfs,    writeStream,    readStream,    buffer = "";mongo.MongoClient.connect("mongodb://localhost/gridfs_test", function (err, db) {    "use strict";    gridfs = Grid(db, mongo);    // write file    writeStream = gridfs.createWriteStream({ filename: "test.txt" });    fs.createReadStream("test.txt").pipe(writeStream);    // after the write is finished    writeStream.on("close", function () {        // read file, buffering data as we go        readStream = gridfs.createReadStream({ filename: "test.txt" });        readStream.on("data", function (chunk) {            buffer += chunk;        });        // dump contents to console when complete        readStream.on("end", function () {            console.log("contents of file:\n\n", buffer);        });    });});

what is cover give an format to file than write or read

const express = require("express");const routes = express.Router();const mongoose = require('mongoose');mongoose.connect("mongodb://localhost:27017/gridfs");var conn = mongoose.connection;var path = require("path");var Grid = require("gridfs-stream");var fs = require("fs");Grid.mongo = mongoose.mongo;var datapath = path.join(__dirname, "../public/1.jpg");conn.once("open",() =>{    console.log('connections is opened ');    console.log(conn.db + "wahab this is running");    var gfs = Grid(conn.db);    var filestream = gfs.createWriteStream({      filename: "wahab.jpg"    });    fs.createReadStream(datapath).pipe(filestream);    filestream.on("close",(file) =>{      console.log(file.filename  + " Write to DB");    }); }); });