Here's an introduction to Node.js, Express, MongoDB, and some basic concepts along with examples:
Introduction to Node.js
Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. It allows you to run JavaScript on the server side.
Event-driven, non-blocking I/O model: Ideal for building scalable network applications.
Package ecosystem (npm): Largest ecosystem of open source libraries in the world.
Basic Ideas on Node.js
Asynchronous: Node.js is designed for asynchronous operations, meaning it can handle many operations at the same time without waiting for any to complete.
Single-threaded: Uses a single thread to handle requests, but can handle many concurrent connections efficiently due to its event-driven architecture.
Express.js
Express.js is a minimal and flexible Node.js web application framework that provides robust features to build single and multi-page, and hybrid web applications.
Middleware: Functions that execute during the lifecycle of a request to the server.
Routing: Define the endpoints and the HTTP methods (GET, POST, etc.).
MongoDB
MongoDB is a NoSQL database that uses a flexible, JSON-like document structure.
NoSQL Database: Does not use traditional table-based relational database structure.
Document-Oriented: Data is stored in collections as BSON (Binary JSON) documents.
Node.js Installation
To install Node.js:
1. Download the installer from [nodejs.org](https://nodejs.org/).
2. Follow the installer instructions.
To verify installation:
node -v
npm -v
Running a JavaScript File in Node.js
Create a file named `app.js`:
console.log('Hello, Node.js!');
Run the file:
node app.js
Server Configuration in Node.js
Create a basic server using the `http` module:
const http = require('http');
const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer((req, res) => {
res.statusCode = 200;
res.setHeader('Content-Type', 'text/plain');
res.end('Hello, World!\n');
});
server.listen(port, hostname, () => {
console.log(`Server running at http://${hostname}:${port}/`);
});
Run the server:
node server.js
Examples
Basic Express Server
const express = require('express');
const app = express();
const port = 3000;
app.get('/', (req, res) => {
res.send('Hello, Express!');
});
app.listen(port, () => {
console.log(`Example app listening at http://localhost:${port}`);
});
Connecting to MongoDB
Using `mongoose` to connect to MongoDB:
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost:27017/mydatabase', {useNewUrlParser: true, useUnifiedTopology: true});
const db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
console.log('Connected to MongoDB');
});
npm Modules
npm (Node Package Manager) is used to manage packages.
Install a package: `npm install package-name`
Install globally: `npm install -g package-name`
Save to dependencies: `npm install package-name --save`
HTTP Module
Basic example using the `http` module:
const http = require('http');
const server = http.createServer((req, res) => {
if (req.method === 'GET' && req.url === '/') {
res.writeHead(200, { 'Content-Type': 'text/plain' });
res.end('Hello, World!');
} else {
res.writeHead(404, { 'Content-Type': 'text/plain' });
res.end('Not Found');
}
});
server.listen(3000, () => {
console.log('Server listening on port 3000');
});
Summary
Node.js: JavaScript runtime for server-side programming.
Express.js: Web framework for Node.js.
MongoDB: NoSQL database.
npm: Package manager for Node.js.
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Server.js
const http=require('http'); const port=4000; const server=http.createServer((req,res)=>{ res.writeHead(200,{'Content-Type': 'text/html'}); res.write(`<ul><li>hello express </li><li>hello php</li></ul>`); res.write('<h3>Thank You have a nice day!</h3>') res.end(); }) server.listen(port,()=>{ console.log(`server is running in the port ${port}`) })
Test.js
var arr=["kolkata","delhi","howrah","punjab","dumdum","patna"]; arr.forEach((val)=>{ console.log(val+"-----"+val.length); })
Test2.js
var arr=[1,2,3,4,5,6,7,8,9,10] var result=arr.map((val)=>{ return val*val; }) console.log(result);
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