Things to keep in mind while writing Backend

npm init 

create .gitignore using web
create .env
create .env.sample its for sample test data

create src source folder
use command line its good practice
use git bash

touch app.js constants.js index.js 

1.Do few things in package.json file
we need import syntax to bring the packages to do so we have to add this

"type":"module"

install nodemon package to restart the project by itself

npm i -D nodemon

we have to add this package.json file in js

 "script":{
    "dev": "nodemon src/index.js"
 }  

crete directory do this inside src

    mkdir controllers db middlewares models routes utils 

we need prettier plugin

npm i -D prettier 

create .prettierrc

     {
         "singleQuote":false,
         "bracketSpacing":true,
         "tabWidth":2 ,
         "trailingComma":"es5",
         "semi":true

    }

create prettierignore

 *.env
 .env
 .env.*
 /.vscode
 /node_modules
 ./dist

install mongoose express and dotenv

npm i mongoose express dotenv

create a file index.js inside the db folder

    import mongoose from "mongoose";
    import {DB_NAME } from "../contants";


 const connectDB = async()=>{
try{
 const connectionInstance = await mongoose.connect(`${process.env.MONGODB_URL}/${DB_NAME}`)
    console.log(`\n MongoDB connected !! DB HOST :${connectionInstance.connection.host}`);
}catch(error){
    console.log("MongoDB Connection Error ",error);
    process.exit(1)
        }
    }


    export default connectDB

bring all your code in index.js

import dotenv from 'dotenv'
import connectDB from './db/index.js';


 connectDB()
    .then(()=>{
        app.listen(process.env.PORT||8000,()=>{
            console.log(` 😁 server is running at PORT ${process.env.PORT}`);
        })

        app.on('error 😣' ,(error)=>{console.error("server failed to start",error);
        });
        
    })
    .catch((error)=>{
        console.log("Mongo DB Connection Failed !!!!",error);    
    })  

install cookie-parser cors

import them in apps

CORS, or Cross-Origin Resource Sharing, is a security feature in web browsers. It controls which websites can access data from other websites. It's used to protect users' data and resources by preventing unauthorized access from malicious websites. CORS allows servers to specify which origins are allowed to access their resources, enabling controlled sharing of data between different domains while maintaining security. In simpler terms, CORS helps keep your data safe on the internet by controlling who can access it from other websites.

inside postman do this to create a user

Open Postman.
Select the HTTP method as POST.
Enter the URL for your endpoint: http://localhost:your_port/api/v1/users/signup (replace your_port with the port number your server is running on).
Go to the "Body" tab.
Select "raw" and choose "JSON" from the dropdown menu.
Enter your JSON data in the text area. For example:

 {
"username": "example_user",
"email": "[email protected]",
"password": "example_password"
}

to login do this

dnt forget this http://localhost:8000/api/v1/auth/login { "email":"[email protected]", "password":"your_password" }