missing db argument error when connecting gridfs multer and mongodb - express

Question

I am using gridfs and mutler to upload files likes ppt pdf etc..to mongodb atlas. When setting up router its keeps saying db not found I have my uri in a config file.What am i missing here in mongodb atlas i have 3 collections in a database called 'test' do i have to create another db in the cluster? Please help
if (!db) throw new Error('missing db argument\nnew Grid(db, mongo)');
^
Error: missing db argument new Grid(db, mongo)
at new Grid (/Users/ezana/Desktop/Canvas/backend/node_modules/gridfs-stream/lib/index.js:25:18)
at Grid (/Users/ezana/Desktop/Canvas/backend/node_modules/gridfs-stream/lib/index.js:19:12)
at Object. (/Users/ezana/Desktop/Canvas/backend/api/routes/fileUploadRoutes.js:9:11)
at Module._compile (internal/modules/cjs/loader.js:701:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
at Module.load (internal/modules/cjs/loader.js:600:32)
at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
at Function.Module._load (internal/modules/cjs/loader.js:531:3)
at Module.require (internal/modules/cjs/loader.js:637:17)
at require (internal/modules/cjs/helpers.js:22:18)
at Object. (/Users/ezana/Desktop/Canvas/backend/app.js:7:21)
at Module._compile (internal/modules/cjs/loader.js:701:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:712:10)
at Module.load (internal/modules/cjs/loader.js:600:32)
at tryModuleLoad (internal/modules/cjs/loader.js:539:12)
at Function.Module._load (internal/modules/cjs/loader.js:531:3)
const router = require('express').Router();
const multer = require('multer');
const db = require('./config/main').mongoURI;
const {
mongo,
connection
} = require('mongoose');
const Grid = require('gridfs-stream');
Grid.mongo = mongo;
const gfs = Grid(connection.db);
const storage = require('multer-gridfs-storage')({
db: connection.db,
file: (req, file) => {
return {
filename: file.originalname
}
}
});

Answer 1

const mongoose = require("mongoose");
const multer = require("multer");
const Grid = require("gridfs-stream");
const GridFsStorage = require("multer-gridfs-storage");
const db = mongoose.connection;
let gfs;
db.once("open", function() {
gfs = Grid(db.db, mongoose.mongo);
});
const storage = new GridFsStorage({
url:
url,
file: (req, file) => {
return new Promise((resolve, reject) => {
crypto.randomBytes(16, (err, buf) => {
if (err) {
return reject(err);
}
const filename = buf.toString("hex") + path.extname(file.originalname);
const fileInfo = {
filename: filename,
bucketName: "uploads"
};
resolve(fileInfo);
});
});
}
});
This worked for me.