node.js - Understanding mongoose connections in express.js -

i learning express.js using following project: https://github.com/scotch-io/easy-node-authentication/tree/linking

in server.js can see , understand following initiates connection database using url database.js:

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

/app/models/user.js contains following:

var mongoose = require('mongoose'); var userschema = mongoose.schema({      local            : {         email        : string,         password     : string,     }, ... } module.exports = mongoose.model('user', userschema); 

finally /config/passport.js contains:

var user = require('../app/models/user'); 

i can see how passport.js obtabs model user.js failing understand how user.js aware of connection setup in server.js initiated object "mongoose" not exported?

what missing?

as can see in file index.js @ last line

var mongoose = module.exports = exports = new mongoose;

this mean, mongoosee export 1 instance (singleton) handler database operations. because first create connection in server.js file, after that, included/require model have connection db server. app work on single object.