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.

Answer 2

create a separate file like database.js and put the code in it:

module.exports = {
  url : 'mongodb://localhost/productecom'
};

and require this file where you need database connection:

like in index.js:

var database = require('./database');
mongoose.connect(database.url);

my example has mongodb and different url, make the change as per your need since I dont know about monk maybe you need to export whole monk configuration., it will work

Answer 3

Just create a simple db.js file with database connection and require your connection whenever you need to use it as follows:

db.js

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

app.js

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

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

index.js

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

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' })
};

Credits to @DrakaSAN who share same concept.