2. Path module , File system and http module - Node.js

1. Path Module

   The path module is used to work with file and directory paths. It provides utilities for handling and transforming file paths in a way that works across operating systems (Windows \ vs Linux /).

const path = require('path')

console.log("Directory name: " , path.dirname(__filename));
console.log("File name: ", path.basename(__filename))
console.log("File extension: ", path.extname(__filename))

const joinPath = path.join("/user" , "document" , "node", "projects")
console.log("Joined Path" , joinPath)

//OUTPUT
Directory name:  C:\Users\rajpu\Desktop\NODE.JS\path-module
File name:  index.js
File extension:  .js
Joined Path \user\document\node\projects

2. File System

   The fs module lets you interact with the file system (read, write, update, delete files/folders). It supports both synchronous and asynchronous (callback/promise) methods.

   • fs.readFile(path, callback) → Reads file (async).

   • fs.readFileSync(path) → Reads file (sync).

   • fs.writeFile(path, data, callback) → Creates/writes file.

   • fs.appendFile(path, data, callback) → Appends to a file

       const fs = require('fs')
       const path = require('path')
     
       const dataFolder = path.join(__dirname , "data") // dir name meh aage data folder jod diya
       if(!fs.existsSync(dataFolder)){
           fs.mkdirSync(dataFolder);
           console.log("Folder is created in current directary")
       }
     
       // Synchorunous way to create file
       const filePath = path.join(dataFolder , "example.txt")
       fs.writeFileSync(filePath , "Hello from nodejs") // data naame ke folder ke andr exapmple.txt ban jaaygi uske ande hello from node.js likh jaayga
       console.log("file created sucessfully")
     
       const readContentFromFile = fs.readFileSync(filePath , "utf8")
       console.log("File Content: " , readContentFromFile)
     
       fs.appendFileSync(filePath , "\n THis is a new line added to the file")
       console.log("New file content: added" )
     
       //Asymshronous way to create file
       const asyncFilePath = path.join(dataFolder , "asyc-file.txt");
       fs.writeFile(asyncFilePath , "Hello Async Node js" , (err)=>{
           if(err) throw err;
           console.log("Asycn file is created sucssfully")
     
           fs.readFile(asyncFilePath , 'utf8' , (err , data)=>{
               if(err) throw err
               console.log("Asycn file content: ",data)
           })
       })
     

3. HTTP Module (http)

   The http module is used to create an HTTP server and handle requests/responses. It is the foundation for creating web servers in Node.js.

   • http.createServer((req, res) => {}) → Creates a server.

   • req.url → URL requested.

   • req.method → HTTP method (GET, POST, etc.).

   • res.writeHead(statusCode, headers) → Set status + headers.

   • res.end(data) → Send response.

       const http = require('http')
     
       const server = http.createServer((req,res)=>{
           console.log(req,"req")
           res.writeHead(200, {"content-type": "text/plain"});
           res.end("Hello nodejs from http module") // this will came in our browser when we run localhost:3000
       })
     
       server.listen(3000 , ()=>{
           console.log("Server is running at port 3000")
       })
     

     How to create routes in https server -: ?

       const http = require('http')
     
       const server = http.createServer((req,res)=>{
           const url = req.url // giev current url of route on which we are having
           if(url === "/"){
               res.writeHead(200 , {"content-type": "text/plain"});
               res.end("Home Page"); //http://localhost:3000/
           }
           else if(url === "/projects"){
               res.writeHead(200 , {"content-type": "text/plain"});
               res.end("Projects Page"); //http://localhost:3000/projects 
           }
           else{
               res.writeHead(404 , {"content-type": "text/plain"});
               res.end("Page Not Found"); //http://localhost:3000/pppppzxoxxn
           }
       })
       server.listen(3000 , ()=>{
           console.log("Server runs at 3000")
       })