passing mongoose as an argument to a function - node.js

Question

I'm developing a node module. I need to pass the mongoose to my module to get three things (mongoose.connection, mongoose.connection.db, mongoose.mongo) out of it.
index.js (myModule - the module I developed)
function myModule(mongoose) {
var db = mongoose.connection;
var gfs = gridfsLockingStream(mongoose.connection.db, mongoose.mongo);
this.someFunction = function() {//some code here}
}
module.exports = myModule;
db.js (A user must use myModule like this)
var mongoose = require('mongoose');
var myModule = require('myModule');
var dbUrl = 'mongodb://localhost:27017/gfsTestDB';
mongoose.connect(dbUrl);
var readyObj = new myModule(mongoose);
module.exports = readyObj; // so that the user can use this everywhere
Then the user can use readyObj to do his/her work.
My problem is that only mongoose.connection is available in myModule function and I get this error(gridfsLockingStreamn cause the error):
Error: missing db argument
new Grid(db, mongo)
I'm using :
"mongodb": "3.0.4",
"mongoose": "4.11.6",
"gridfs-locking-stream": "1.1.1",
"gridfs-stream": "1.1.1",
One solution (idea from #GrégoryNEUT) (but I think it's not the correct way):
index.js no changes
db.js using promise and mongoose event handler
var mongoose = require('mongoose');
var myModule = require('myModule');
var dbUrl = 'mongodb://localhost:27017/gfsTestDB';
mongoose.connect(dbUrl);
module.exports = new Promise(function (resolve, reject) {
mongoose.connection.on('connected', function () {
var readyObj = new myModule(mongoose);
resolve(readyObj);
});
});
photoRouter.js (one of the user's files - the user want to use readyObj)
var readyObj = require('./db').then(function (readyObj) {
// then the user uses readyObj
}
Can the code be improved?

Answer 1

Looking at the documentation of mongoose connect
You can use of Promises.
var mongoose = require('mongoose');
var myModule = require('myModule');
var dbUrl = 'mongodb://localhost:27017/gfsTestDB';
mongoose.connect(dbUrl)
.then(
// The connection is ready to use!
() => {
var readyObj = new myModule(mongoose);
// ...
},
// Handle the connection error
(err) => {
// ...
},
);
You can use of Callbacks
var mongoose = require('mongoose');
var myModule = require('myModule');
var dbUrl = 'mongodb://localhost:27017/gfsTestDB';
mongoose.connect(dbUrl, (err) => {
if (err) {
// Handle the error
// ...
return;
}
// We get successfully connected to the database
var readyObj = new myModule(mongoose);
// ...
});