了解express.js中的猫鼬连接

Question

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

In server.js I can see and understand the following initiates a connection to the database using the url from database.js:

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

/app/models/user.js contains the 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 the model from user.js however I am failing to understand how user.js is aware of the connection setup in server.js as the initiated object "mongoose" is not exported?

What am I missing?

Answer 1

as you can see in this file index.js at the last line

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

this mean, Mongoosee will export only one instance (singleton) to handler database operations. because you first create connection in your server.js file, after that, any included/require model will have connection to your db server. all app will work on single object.