aditechdev / nodejs-tut

https://nodejs.org/dist/latest-v18.x/docs/api/

node ./index.js -> To Run the command

console.log("SSUB"); --> PRINT console.warn(""); --> PRINT

== -> Match the Value eg: "20" == 20 true

=== -> Match the value and type eg: "20" is not equal to 20

Create Array const arr = [1,2,3,4]; console.log(arr[0])

Exxport module.exports={

x: 10,
y:20

}

Import const app = require('./app');

Create file const fs = require('fs'); fs.writeFileSync("hellow.txt", "Hey yes")

// To know the directory name console.log(__dirname); // To know the directory name

console.log(__filename);

// Create serve const http = require('http');

http.createServer((req, res) =>{ res.write("

THID IS AWESOME

"); res.end(); }).listen(4500);

npm install --> To Get Node Module

install sudo npm install -g --force nodemon

NodeJs is Single threaded and async

// TO CREAT FILE

const input = process.argv; if (input[2] == "add") {

fs.writeFileSync(input[3], input[4])

} else if (input[2] == "remove") {

fs.unlinkSync(input[3]);

} else { console.log("Invalid Input"); } ---------- CONSOLE ------------------------ node index.js add orange.txt 'heloo orrage'

node index.js remove orange.txt

---

Create file inside directory

const dirPath = path.join(__dirname, 'files'); console.log(dirPath) for (let index = 0; index < 5; index++) { // const element = array[index]; fs.writeFileSync(dirPath+"/Hello"+index+".txt", "a simple text file");

}

---

read file fs.readdir(dirPath,(errr, files)=> { console.warn(files) });

---

CRUD WITH FILE SYSTEM

READ const filePath = ${dirPath}/aplle.txt

fs.readFile(filePath,'utf8',(err, filePath)=> { console.log(filePath); });

UPDATE

fs.appendFile(filePath, ' and file name is apple.txt ', (err) => { console.log(err); })

RENAME FILE fs.rename(filePath, ${dirPath}/alpha.txt, (err) => { console.log(err); })

DELETE

fs.unlinkSync(filePath);

---

Buffer

A SMALL memory required by nodeJs to Perform operation

---

TO DELAY A RESPONSE console.log("oKK"); setTimeout(() => { console.log("oKK2");

}, 2000); console.log("oKK3");

---

PROMISE

let a = 20; let b = 0;

let waitingData = new Promise((resolve, reject) => { setTimeout(() => { // b = 20; resolve(30); }, 2000); })

waitingData.then((data) => { b = data; console.log(a + b);

})

---

HOW NODE JS WORK CALL BACK API CALLbACK QUEUE

THis is called EVENT LOOP CALL StACK -> NODE API ! CALLBACK QUUE

---

Create Simple API

const express = require('express');

const app = express();

app.get( '', (req, res) => { console.log("SEND FROM BROWSER"+ req.query.name); res.send("HELLO THiS IS HOMEPAGE " +req.query.name); } );

app.get('/about', (req, res) => { res.send("THIS IS ABOUT PAGE "); }) app.get('/help', (req, res) => { res.send("THIS IS HELP PAGE "); })

app.listen(4500, () => { console.log('App listening on port 3000!'); });

---

GET HTML INSIDE

const express = require('express'); const path = require('path');

const app = express(); const publicPath = path.join(__dirname, 'public') console.log(publicPath);

app.use(express.static(publicPath))

app.listen(4500)

SET ERROR PAGE const express = require('express'); const path = require('path');

const app = express(); const publicPath = path.join(__dirname, 'public') console.log(publicPath);

// app.use(express.static(publicPath)) app.get('', (, res) => { res.sendFile(${publicPath}/index.html) }); app.get('/about', (, res) => { res.sendFile(${publicPath}/about.html) }); app.get('*', (_, res) => { res.sendFile(${publicPath}/nopaage.html) });

app.listen(4500)

---

Use template engine

Create file like this views/profile.ejs

in index.js app.set('view engine', 'ejs'); app.get('/profile', (_, res) => { res.render('profile'); })

---

Application level Middle Ware

const reqFilter = (req, res, next) => { if (!req.query.age) { res.send("PLEASE PROVEDE AFE"); }else if (req.query.age < 18) { res.send("Below Age"); } else { next();

}
// console.log('reqfilter');

}

app.use(reqFilter);

---

Route Level Middleware const { profile } = require('console'); const express = require('express'); const path = require('path'); const reqfilter = require('./middleware') const route = express.Router();

const app = express();

route.use(reqfilter);

// app.use(reqFilter);

app.get('/',(req, res) => {

res.send("WELCOME TO HOMEPAGE");

}); route.get('/help',(req, res) => {

res.send("WELCOME TO HOMEPAGE");

}); route.get('/profile',(req, res) => {

res.send("WELCOME TO HOMEPAGE");

}); route.get('/about',(req, res) => {

res.send("WELCOME TO HOMEPAGE");

}); app.get('/contact',(req, res) => {

res.send("WELCOME TO HOMEPAGE");

});

app.use('/',route);

app.listen(4500)

install mongodb https://www.youtube.com/watch?v=s1WQ0eEpqqg https://www.youtube.com/watch?v=NLw7Tln6IeM brew services restart mongodb/brew/mongodb-community

mongosh show dbs -> to view db exit

use youtube db.createCollection('playlist') show collections

db.playlist.drop() --> Remove collection db.dropDatabase() -- > Remove database

insert data in collection db.product.insertOne({name: "M31", brand: "Samsung", price: "25000", category: "mobile"})

to display data db.product.find()

to update one db.product.updateOne({name:"N91"},{$set:{brand:'OPPO'}})

db.product.deleteOne({brand:"OPPO"})

--------------CONNECT MONGO DP TO NODE----------------

const { MongoClient } = require('mongodb'); const url = 'mongodb://localhost:27017';

const database = "e-comm";

const client =new MongoClient(url);

async function getData() { let results = await client.connect(); let db = results.db(database); let collection = db.collection("product"); let response = await collection.find({}).toArray(); console.log(response); }

getData();