1. Basics

• Installation: Download from Node.js official website.
• Check Version:

node -v
npm -v

2. Creating a Simple Server

const http = require('http');
const server = http.createServer((req, res) => {
    res.statusCode = 200;
    res.setHeader('Content-Type', 'text/plain');
    res.end('Hello, World!n');
});
server.listen(3000, '127.0.0.1', () => {
    console.log('Server running at http://127.0.0.1:3000/');
});

3. File System Operations

• Read File:
  
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  const fs = require('fs');
  fs.readFile('example.txt', 'utf8', (err, data) => {
      if (err) throw err;
      console.log(data);
  });
  
  

• Write File:
  
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  fs.writeFile('example.txt', 'Hello, Node!', (err) => {
      if (err) throw err;
      console.log('File has been saved!');
  });
  
  

4. Modules

• Create a Module:
  
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  // myModule.js
  const greeting = (name) => `Hello, ${name}!`;
  module.exports = greeting;
  
  

• Import a Module:
  
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  const greeting = require('./myModule');
  console.log(greeting('World'));
  
  

5. NPM Commands

• Initialize Project:
  
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  npm init
  

• Install Package:
  
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  npm install package-name
  

• Uninstall Package:
  
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  npm uninstall package-name
  

• List Installed Packages:
  
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  npm list
  

6. Asynchronous Programming

• Callback Example:
  
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  function fetchData(callback) {
      setTimeout(() => {
          callback('Data fetched');
      }, 1000);
  }
  fetchData((data) => {
      console.log(data);
  });
  
  

• Promises:
  
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  const fetchData = () => {
      return new Promise((resolve, reject) => {
          setTimeout(() => {
              resolve('Data fetched');
          }, 1000);
      });
  };
  fetchData().then(data => console.log(data));
  
  

• Async/Await:
  
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  const fetchData = async () => {
      return 'Data fetched';
  };
  const getData = async () => {
      const data = await fetchData();
      console.log(data);
  };
  getData();
  
  

7. Express.js Framework

• Setting Up Express:
  
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  npm install express
  

• Basic Express Server:
  
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  const express = require('express');
  const app = express();
  app.get('/', (req, res) => {
      res.send('Hello, Express!');
  });
  app.listen(3000, () => {
      console.log('Server running on http://localhost:3000');
  });
  
  

8. Debugging

• Debug with Node:
  
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  node inspect yourfile.js
  

• Using Chrome DevTools:
  
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  node --inspect yourfile.js
  

9. Commonly Used Modules

• Path:
  
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  const path = require('path');
  console.log(path.join(__dirname, 'file.txt'));
  
  

• OS:
  
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  const os = require('os');
  console.log(os.platform());
  
  

• HTTP:
  
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  const http = require('http');
  

10. Tips

• Use nodemon for auto-reloading during development:
  
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  npm install -g nodemon
  nodemon yourfile.js
  
  

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