Why didn't I need to connect to database - node.js

Question

I am new to web development. I just made a user model and then required into the main app.js file. But I saw that while making the user model I didn't need to connect to the database for it but I have connected the database to the app.js file. Then I saw how to require() works I found that it first runs the module/file which we had required and then return the object which that file returns. So I thought that it must throw an error because it wouldn't have fount the connection to the database while making the user model.
var mongoose=require('mongoose');
var passportlocalmongoose=require('passport-local-mongoose');
var userschema=new mongoose.Schema({
username:String,
password:String
});
userschema.plugin(passportlocalmongoose);
module.exports=mongoose.model('User',userschema);

Answer 1

you're not connected because you're not providing the required parameter,
here , there are some steps you can use.
first of all install express, mongoose and dotenv dependencies, and you will need a database URL in .env file
import express from 'express';
import dotenv from 'dotenv';
import mongoose from 'mongoose';
const app = express();
dotenv.config();
mongoose.connect(process.env.DATABASE_URL, {
useNewUrlParser: true,
useUnifiedTopology: true,
useCreateIndex: true,
useFindAndModify: false,
})
.then(() => process.stdout.write('DB Connection succesfully\n'));
const port =3000
app.listen(port, () => process.stdout.write(`Listening on port ${port} ... \n`));
export default app;