NodeJS

Introduction:

"Node.js introduced me to the world of backend development and server-side scripting." 

Node.js is a runtime environment that allows developers to write server-side applications using JavaScript. With Node.js, I explored building RESTful APIs, handling server requests, and managing databases.

Key Topics Learned

1. Introduction to Node.js:

   • Setting up a Node.js environment.

   • Understanding modules (require and exports) and npm.

// Setting up Node.js Environment

console.log("Node.js is running!");

// Modules

const fs = require("fs"); // Built-in module

fs.writeFileSync("example.txt", "Hello, Node.js!");

// Exporting and Importing

// file1.js

module.exports.greet = () => console.log("Hello from module!");

// file2.js

const { greet } = require("./file1");

greet();

2. HTTP and Express.js:

   • Setting up servers using the built-in http module.

   • Using Express.js to create routes and handle requests.

// HTTP Module Server

const http = require("http");

const server = http.createServer((req, res) => {

  res.writeHead(200, { "Content-Type": "text/plain" });

  res.end("Hello, World!");

});

server.listen(3000, () => console.log("Server running on port 3000"));

// Express.js Server

const express = require("express");

const app = express();

app.get("/", (req, res) => res.send("Hello, Express!"));

app.listen(3000, () => console.log("Express server running on port 3000"));

3. Middleware:

   • Using middleware functions in Express for logging, authentication, and data validation.

// Middleware Example

const app = express();

// Logger Middleware

app.use((req, res, next) => {

  console.log(`${req.method} ${req.url}`);

  next();

});

// Authentication Middleware

const authenticate = (req, res, next) => {

  const token = req.headers.authorization;

  if (token === "12345") {

    next();

  } else {

    res.status(401).send("Unauthorized");

  }

};

app.use(authenticate);

4. Working with APIs:

   • Creating RESTful APIs for CRUD operations.

   • Handling JSON data and requests using body-parser or Express’s built-in middleware.

// RESTful API with CRUD Operations

const app = express();

app.use(express.json()); // Built-in middleware for JSON parsing

let data = [];

// Create

app.post("/data", (req, res) => {

  data.push(req.body);

  res.status(201).send("Data added!");

});

// Read

app.get("/data", (req, res) => res.json(data));

// Update

app.put("/data/:id", (req, res) => {

  const id = req.params.id;

  data[id] = req.body;

  res.send("Data updated!");

});

// Delete

app.delete("/data/:id", (req, res) => {

  const id = req.params.id;

  data.splice(id, 1);

  res.send("Data deleted!");

});

app.listen(3000, () => console.log("API running on port 3000"));

5. Database Integration:

   • Connecting to databases like SQL.

// Connecting to SQL Database

const mysql = require("mysql");

const connection = mysql.createConnection({

  host: "localhost",

  user: "root",

  password: "password",

  database: "exampleDB",

});

connection.connect((err) => {

  if (err) throw err;

  console.log("Connected to SQL database!");

  // Sample Query

  connection.query("SELECT * FROM users", (err, results) => {

    if (err) throw err;

    console.log(results);

  });

});