How does the model know which mongo connection to use?

Question

JavaScript

spoiler

var mongoose = require('mongoose');
mongoose.connect("mongodb://localhost/test");
var User = require(__dirname + '/models/User.js');

spoiler

User.js content

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var userSchema = new Schema({
    id: {
        type: Number,
        unique: true,
    },
});
module.exports = mongoose.model('User', userSchema);

After such code, I can use the model, select from the database and save, but how does she know that I need to use this particular connection from above, because these two variables and User and mongoose are not connected at all. Immediately the question is how can I, for example, then in one application take users from two different databases, for example, according to one model.

Answer 1

I'll try to feel myself in the role of Vanga. Between the 2nd and 3rd line of code somewhere should be something like this:

const UserSchema = new mongoose.Schema({...});
module.exports = mongoose.model("User", UserSchema);