How to acess db connection in whole app in node.js?

Question

I connect mongodb with monk in app.js

var express = require('express');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var mongo = require('mongodb');
var monk = require('monk');
var db = monk('localhost:27017/nodetest1');

app.use(function(req,res,next){
  req.db = db;
  next();
});

It working fine here . But now I add index.js in routes folder

var monk = require('monk');
var db = monk('localhost:27017/nodetest1');

exports.index = function(req, res){
  var collection = db.get('usercollection');
  collection.find({},{},function(e,docs){
  res.render('userlist', { "userlist" : docs});
});
res.render('index', { title: 'Express' })
};

It also working fine. But I am connecting DB both in app.js and index.js . Which thing I need to do that connection define in app.js is accessible in index.js

Answer 1

The two solution I know are:

Put the connection in another file, import that file.

db.js

var monk = require('monk');
module.exports = monk('localhost:27017/nodetest1');

Other files:

var db = require('./db.js');

Or pass the same connection around:

app.js:

var monk = require('monk');
var db = monk('localhost:27017/nodetest1');
var module = require('./myModule.js')(db);

myModule.js:

module.exports = (db) => {
    //...
};

Or:

app.js:

var monk = require('monk');
var db = monk('localhost:27017/nodetest1');
var module = require('./myModule.js');
module.init(db);

myModule.js:

var db;

exports.init = (masterDb) => {
    db = masterDb;
};

And ensuring db is set before using it.