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main.js

const SHA256 = require('crypto-js/sha256');

class Block {
	
	constructor(index, timestamp, data, prevHash = '') {
		this.index = index;
		this.timestamp = timestamp;
		this.data = data;
		this.prevHash = prevHash;
		this.hash = this.calculateHash();
	}
	
	calculateHash() {
		return SHA256(this.index + this.prevHash + this.timestamp + JSON.stringify(this.data)).toString();
	}
	
}

class Blockchain {
	constructor() {
		this.chain = [this.createGenesisBlock()];
	}
	
	createGenesisBlock() {
		return new Block(0, "01/01/2021", "Genesis block", "0");
	}
	
	getLatestBlock() {
		return this.chain[this.chain.length - 1];
	}
	
	addBlock(newBlock) {
			newBlock.prevHash = this.getLatestBlock().hash;
			newBlock.hash = newBlock.calculateHash();
			this.chain.push(newBlock);
	}
	
	isChainValid() {
		for(let i=1; i < this.chain.length; i++) {
			const currentBlock = this.chain[i];
			const prevBlock = this.chain[i-1];
			
			if(currentBlock.hash !== currentBlock.calculateHash()) {
				return false;
			}
			
			if(currentBlock.prevHash != prevBlock.hash) {
				return false;
			}
		}
		
		return true;
	}
	
}

let tcoin = new Blockchain();
tcoin.addBlock(new Block(1, "03/09/2021", {amt: 100}));
tcoin.addBlock(new Block(1, "04/09/2021", {amt: 200}));

console.log(tcoin.isChainValid());
console.log(JSON.stringify(tcoin, null, 4));

//tempering data
tcoin.chain[2].amt = 2000;
console.log(JSON.stringify(tcoin, null, 4));
console.log(tcoin.isChainValid());

Proof of Work

const SHA256 = require('crypto-js/sha256');

class Block {
	
	constructor(index, timestamp, data, prevHash = '') {
		this.index = index;
		this.timestamp = timestamp;
		this.data = data;
		this.prevHash = prevHash;
		this.hash = this.calculateHash();
		this.nonce = 0;
	}
	
	calculateHash() {
		return SHA256(this.index + this.prevHash + this.timestamp + JSON.stringify(this.data) + this.nonce).toString();
	}
	
	mineBlock(complexity) {
		while(this.hash.substring(0, complexity) !== Array(complexity + 1).join("0")) {
			this.nonce++;
			//console.log(this.nonce);
			this.hash = this.calculateHash();
		}
		
		console.log(`Block mined: ${this.hash}`);
	}
	
}

class Blockchain {
	constructor(complexity = 0) {
		this.chain = [this.createGenesisBlock()];
		this.complexity = complexity;
	}
	
	createGenesisBlock() {
		return new Block(0, "01/01/2021", "Genesis block", "0");
	}
	
	getLatestBlock() {
		return this.chain[this.chain.length - 1];
	}
	
	addBlock(newBlock) {
			newBlock.prevHash = this.getLatestBlock().hash;
			//newBlock.hash = newBlock.calculateHash();
			newBlock.mineBlock(this.complexity);
			this.chain.push(newBlock);
	}
	
	isChainValid() {
		for(let i=1; i < this.chain.length; i++) {
			const currentBlock = this.chain[i];
			const prevBlock = this.chain[i-1];
			
			if(currentBlock.hash !== currentBlock.calculateHash()) {
				return false;
			}
			
			if(currentBlock.prevHash != prevBlock.hash) {
				return false;
			}
		}
		
		return true;
	}
	
}

let tcoin = new Blockchain(5);

console.log("Mining Block 1...");
tcoin.addBlock(new Block(1, "03/09/2021", {amt: 100}));

console.log("Mining Block 2...");
tcoin.addBlock(new Block(1, "04/09/2021", {amt: 200}));

console.log(JSON.stringify(tcoin, null, 4));

Playground for practice https://regexr.com/ https://regex101.com/

Pattern Matching

Regex Syntax

/<regex pattern>/

Starts with wild card character

^

Ends with wcc

$

set enclosed in

[set]
[^invert-set]

only numbers

^[0-9]+$
^\d+$

only characters

^[a-zA-Z]+$
^\w+$

occurance wcc

* => any number of occurrence
? => 0 or 1 occurrence
+ => 1 or many occurrence

e.g. adarsh mishra
to match 1 space /adarsh\smishra/
to match multiple space /adarsh\s+mishra/
to match 0 or many spaces /adarsh\s*mishra/

no special characters

^[0-9a-zA-Z\s]+$

limited characters or numbers

^[0-9]{6}$
^[a-z]{3}$

min / max range characters or numbers

^[0-9]{3,6}$
^[a-z]{3,6}$

OR clause

^(chacha|bhatija)$

case insensitive

//i

global check

//g

search any pattern
(.) e.g. “https://www.youtube.com/watch?v=hw_HpTI_Wkw”.match(/v=(.)/)[1]

will return video id hw_HpTI_Wkw

Assignment

1. girls / boys name
2. phone number
3. find Indian zip code
4. valid name
5. email id
6. 8-12 character password
7. aadhaar number
8. pancard
9. name starts with vowels
10. names ends with vowels
11. names having only 5 characters
12. credit card number

Sample Text

1234567890
123453
DAVPS0412P
127836320613
9876543210
098762
xyz@yahoo.com
smita
&UJMmju7
shailesh
143258761937
priyanka
abc@gmail.com
112096851365
%TGBbgt5
priya

To get the connection string

Atlas > Deployment > Databases > Connect > Connect your application > Driver Node.js > Version 4.1 or later

CRUD Application using Vanilla JS | HTML5 | CSS3 | Bootstrap5

NOTE: DON’T FORGET TO APPEND DATABASE NAME IN CONNECTION STRING URL

users_module.js

//Step 1: Database connection using connection string
const mongoose = require("mongoose");

//mongodb://127.0.0.1:27017/dbname
//const conn_str = "mongodb://localhost:27017/tcet";
const conn_str = "mongodb+srv://user:passwd@cluster0.gp5lcta.mongodb.net/<DBNAME>?retryWrites=true&w=majority"

mongoose.connect(conn_str, { useNewUrlParser: true, useUnifiedTopology: true })
	.then(() => console.log("Connected successfully..."))
	.catch( (error) => console.log(error) );
	
	
//Step 2: Create Schema (similar to Java Class)
const userSchema = new mongoose.Schema({
	name: String,
	age: Number,
	city: String
})

//Step 3: Create collection Object (model)
// MAPPING 
const userObject = new mongoose.model("users", userSchema);

exports.User = userObject;

Test Database Connection

index.js

const express = require("express");
const port = 8080;

const user_model = require("./users_module");
const User = user_model.User;

const app = express();
app.use(express.json());

var cors = require('cors');
app.use(cors());

app.get("/", (req, res) => {
	res.send("Hello Friends..");
});

app.get("/user", async (req, res) => {
	let data = await User.find().sort({_id:-1});
	res.send(data);
});

app.get("/user/:id", async (req, res) => {
	console.log(req.params.id);
	let data = await User.find({"_id": req.params.id});
	res.send(data[0]);
});

app.post("/user", async (req, res) => {
	console.log(req.body)
	let u = await User(req.body);
	let result = u.save();
	res.send(req.body);
});

app.put("/user", async (req, res) => {
	console.log(req.body);
	
	//User.updateOne({where}, {set});
	let u_data = await User.updateOne({"_id": req.body._id}, {
		"$set": {
			"name" : req.body.name,
			"age" : req.body.age,
			"city" : req.body.city
		}
	});
	
	res.send(u_data);
});

app.delete("/user", async(req, res) => {
	
	let d_data = await User.deleteOne({"_id": req.body._id});
	res.send(d_data);
});

app.listen(process.env.PORT || port, () => {	
	console.log(`Listening on port ${port}`);
});

Run index.js file (node .) and Test in Postman

GET Method

POST Method

PUT Method

DELETE Method

Create Frontend to access all web services from Web Browser

script.js

//const api_url = "<heroku_app_url>"
const api_url = "http://localhost:8080/user"

function loadData(records = []) {
	var table_data = "";
	for(let i=0; i<records.length; i++) {
		table_data += `<tr>`;
		table_data += `<td>${records[i].name}</td>`;
		table_data += `<td>${records[i].age}</td>`;
		table_data += `<td>${records[i].city}</td>`;
		table_data += `<td>`;
		table_data += `<a href="edit.html?id=${records[i]._id}"><button class="btn btn-primary">Edit</button></a>`;
		table_data += '&nbsp;&nbsp;';
		table_data += `<button class="btn btn-danger" onclick=deleteData('${records[i]._id}')>Delete</button>`;
		table_data += `</td>`;
		table_data += `</tr>`;
	}
	//console.log(table_data);
	document.getElementById("tbody").innerHTML = table_data;
}

function getData() {
	fetch(api_url)
	.then((response) => response.json())
	.then((data) => { 
		console.table(data); 
		loadData(data);
	});
}


function getDataById(id) {
	fetch(`${api_url}/${id}`)
	.then((response) => response.json())
	.then((data) => { 
	
		console.log(data);
		document.getElementById("id").value = data._id;
		document.getElementById("name").value = data.name;
		document.getElementById("age").value = data.age;
		document.getElementById("city").value = data.city;
	})
}


function postData() {
	var name = document.getElementById("name").value;
	var age = document.getElementById("age").value;
	var city = document.getElementById("city").value;
	
	data = {name: name, age: age, city: city};
	
	fetch(api_url, {
		method: "POST",
		headers: {
		  'Accept': 'application/json',
		  'Content-Type': 'application/json'
		},
		body: JSON.stringify(data)
	})
	.then((response) => response.json())
	.then((data) => { 
		console.log(data); 
		window.location.href = "index.html";
	})
}	


function putData() {
	
	var _id = document.getElementById("id").value;
	var name = document.getElementById("name").value;
	var age = document.getElementById("age").value;
	var city = document.getElementById("city").value;
	
	data = {_id: _id, name: name, age: age, city: city};
	
	fetch(api_url, {
		method: "PUT",
		headers: {
		  'Accept': 'application/json',
		  'Content-Type': 'application/json'
		},
		body: JSON.stringify(data)
	})
	.then((response) => response.json())
	.then((data) => { 
		console.table(data);
		window.location.href = "index.html";
	})
}


function deleteData(id) {
	user_input = confirm("Are you sure you want to delete this record?");
	if(user_input) {
		fetch(api_url, {
			method: "DELETE",
			headers: {
			  'Accept': 'application/json',
			  'Content-Type': 'application/json'
			},
			body: JSON.stringify({"_id": id})
		})
		.then((response) => response.json())
		.then((data) => { 
			console.log(data); 
			window.location.reload();
		})
	}
}

index.html

<!DOCTYPE html>
<html>
	<head>
		<title>CIA Institute - MongoDB Project</title>
		<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" crossorigin="anonymous">
		<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js"crossorigin="anonymous"></script>
	</head>
	<body class="d-flex flex-column h-100 container">
		<header>
			<nav class="navbar navbar-expand-lg navbar-expand-sm navbar-light bg-light">
			  <div class="container-fluid">
				<div class="collapse navbar-collapse" id="navbarNavAltMarkup">
				  <div class="navbar-nav">
					<a class="nav-link active" aria-current="page" href="#">Listing</a>
					<a class="nav-link" href="add.html">Add New</a>
				  </div>
				</div>
			  </div>
			</nav>
		</header>
		
		<table class="table table-striped table-hover text-center">
			<thead>
				<th>Name</th>
				<th>Age</th>
				<th>City</th>
				<th>Action</th>
			</thead>
			<tbody id="tbody">
				
			</tbody>
			<tfoot>
				
			</tfoot>
		</table>
		
		<footer class="footer mt-auto py-3 bg-light">
		  <div class="container text-center">
			<span class="text-muted"> &copy; CIA Institute 2022</span>
		  </div>
		</footer>
	</body>
	<script src="script.js"></script>
	<script>
		getData();
	</script>
</html>

Test in Browser

add.html

<html>
	<head>
		<title>CIA Institute - MongoDB Project</title>
		<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" crossorigin="anonymous">
		<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js"crossorigin="anonymous"></script>
	</head>
	<body class="d-flex flex-column h-100 container">
		<header>
			<nav class="navbar navbar-expand-lg navbar-expand-sm navbar-light bg-light">
			  <div class="container-fluid">
				<div class="collapse navbar-collapse" id="navbarNavAltMarkup">
				  <div class="navbar-nav">
					<a class="nav-link" href="index.html">Listing</a>
					<a class="nav-link active" aria-current="page" href="add.html">Add New</a>
				  </div>
				</div>
			  </div>
			</nav>
		</header>
		
		<h3>Add Document</h3>
		
		<form onsubmit="return false;">
		  <div class="mb-3">
			<label for="name" class="form-label">Name</label>
			<input type="text" class="form-control" id="name" autofocus>
		  </div>
		  <div class="mb-3">
			<label for="exampleInputPassword1" class="form-label">Age</label>
			<input type="text" class="form-control" id="age">
		  </div>
		  <div class="mb-3">
			<label for="city" class="form-label">City</label>
			<input type="text" class="form-control" id="city">
		  </div>
		  <button class="btn btn-primary" onclick="return postData()">Submit</button>
		  <a href="index.html" class="btn btn-primary">Cancel</a>
		</form>
		
		<footer class="footer mt-auto py-3 bg-light">
		  <div class="container text-center">
			<span class="text-muted"> &copy; CIA Institute 2022</span>
		  </div>
		</footer>
	</body>
	<script src="script.js"></script>
	<script>
	</script>
</html>

edit.html

<html>
	<head>
		<title>CIA Institute - MongoDB Project</title>
		<link href="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/css/bootstrap.min.css" rel="stylesheet" crossorigin="anonymous">
		<script src="https://cdn.jsdelivr.net/npm/bootstrap@5.0.2/dist/js/bootstrap.bundle.min.js"crossorigin="anonymous"></script>
	</head>
	<body class="d-flex flex-column h-100 container">
		<header>
			<nav class="navbar navbar-expand-lg navbar-expand-sm navbar-light bg-light">
			  <div class="container-fluid">
				<div class="collapse navbar-collapse" id="navbarNavAltMarkup">
				  <div class="navbar-nav">
					<a class="nav-link" href="index.html">Listing</a>
					<a class="nav-link active" aria-current="page" href="add.html">Add New</a>
				  </div>
				</div>
			  </div>
			</nav>
		</header>
		<h3>Edit Document</h3>
		<form onsubmit="return false;">
			<input type="hidden" class="form-control" id="id">
		  <div class="mb-3">
			<label for="name" class="form-label">Name</label>
			<input type="text" class="form-control" id="name" autofocus>
		  </div>
		  <div class="mb-3">
			<label for="exampleInputPassword1" class="form-label">Age</label>
			<input type="text" class="form-control" id="age">
		  </div>
		  <div class="mb-3">
			<label for="city" class="form-label">City</label>
			<input type="text" class="form-control" id="city">
		  </div>
		  <button class="btn btn-primary" onclick="return putData()">Update</button>
		  <a href="index.html" class="btn btn-primary">Cancel</a>
		</form>
		
		<footer class="footer mt-auto py-3 bg-light">
		  <div class="container text-center">
			<span class="text-muted"> &copy; CIA Institute 2022</span>
		  </div>
		</footer>
	</body>
	<script src="script.js"></script>
	<script>
		const urlParams = new URLSearchParams(window.location.search);
		const id = urlParams.get('id');
		getDataById(id);
	</script>
</html>

Screenshots

Reference Link: https://gitlab.com/tcet/mongodb-july-21.git

Create REST Api using Node.js | Express | Mongoose

index.js

const port = 8080;
const mongoose = require("mongoose");
//const conn_str ="C"
const conn_str = "mongodb://<user>:<passwd>@cluster0-shard-00-00.dslyw.mongodb.net:27017,cluster0-shard-00-01.dslyw.mongodb.net:27017,cluster0-shard-00-02.dslyw.mongodb.net:27017/<databasename>?ssl=true&replicaSet=atlas-3xk2hf-shard-0&authSource=admin&retryWrites=true&w=majority";


mongoose.connect(conn_str, { useNewUrlParser: true , useUnifiedTopology: true})
	.then( () => console.log("Connected successfully...") )
	.catch( (err) => console.log(err) );


const userSchema = new mongoose.Schema({
	name: String,
	age: Number,
	city: String
});

const user = new mongoose.model("users", userSchema);


/** Express Mongoose Integration **/

const express = require("express");
var cors = require('cors');
const app = express();


//add middlewares
app.use(express.json());
app.use(cors());


app.route("/user")
.get(async (req, res) => {
	let data = await user.find();
	res.send(data);
})
.post(async (req, res) => {
	req_data = req.query;
	let obj = new user(req.query)
	let result = await obj.save();
	res.send(result);
})
.put(async (req, res) => {
	console.log(req.body);
	
	//model.updateOne({where}, {set});
	let u_data = await user.updateOne({"_id": req.body._id}, {
		"$set": {
			"name" : req.body.name,
			"age" : req.body.age,
			"city" : req.body.city
		}
	});
	
	res.send(u_data);
})
.delete(async (req, res) => {
	let d_data = await User.deleteOne({"_id": req.body._id});
	res.send(d_data);
})


app.listen(process.env.PORT || port, () => {
	console.log("listening 8080...");
});

Call REST Api using Vanilla JS

index.html

<script>
function getDataById(id) {
	fetch(`http://localhost:8080/user/${id}`)
	.then((response) => response.json())
	.then((data) => { console.table(data); })
}

function getData() {
	fetch("http://localhost:8080/user")
	.then((response) => response.json())
	.then((data) => { console.table(data); })
}

function postData(data) {
	fetch("http://localhost:8080/user", {
		method: "POST",
		headers: {
		  'Accept': 'application/json',
		  'Content-Type': 'application/json'
		},
		body: JSON.stringify(data)
	})
	.then((response) => response.json())
	.then((data) => { console.table(data); })
}
	

function putData(data) {
	fetch("http://localhost:8080/user", {
		method: "PUT",
		headers: {
		  'Accept': 'application/json',
		  'Content-Type': 'application/json'
		},
		body: JSON.stringify(data)
	})
	.then((response) => response.json())
	.then((data) => { console.table(data); })
}

function deleteData(id) {
	fetch("http://localhost:8080/user", {
		method: "DELETE",
		headers: {
		  'Accept': 'application/json',
		  'Content-Type': 'application/json'
		},
		body: JSON.stringify({"_id": id})
	})
	.then((response) => response.json())
	.then((data) => { console.table(data); })
}


getDataById();
getData();
postData({"name": "Akshu", "age": 20, "city": "Koradi"});
putData({"_id" : "61082ae9cd4b7a0ccc39d377", "name": "chaitu"});
deleteData("61082b4ecd4b7a0ccc39d37a");
</script>

Signup/Signin on heorku

https://herokuapp.com/

Login from terminal (Make sure you have installed heroku cli – https://devcenter.heroku.com/articles/heroku-cli#download-and-install)

heroku login

Create app.js

const express = require("express");
const app = express();
const port = 8080;

app.get("/", (req, res) => {
    res.send("Hello Heroku");
})

app.listen(process.env.PORT || port, () => {
	console.log("listening 8080...");
});

process.env.PORT this will be provided by heroku server

Test locally by running following command

node app.js
OR
nodemon app.js

If you get any error e.g. module not found you can install those module using npm

npm install <module_name>

To find installed module version

npm view <module_name> version
e.g.
npm view express version

Create package.json

{
	"scripts" : {
		"start" : "node app.js"
	},
	"dependencies": {
		"express": "4.17.1",
		"mongoose": "5.13.3",
		"cors": "2.8.5"
	}
}

Run following command from terminal

#onetime
git init

#onetime
heroku create <yournewappname>

Run git commands

git add .
git commit -m 'msg'

#to verify origin
git config -l

#if you are not able to see url and fetch then run git remote add origin 
#remote.heroku.url=https://git.heroku.com/project.git
#remote.heroku.fetch=+refs/heads/*:refs/remotes/heroku/*
#git remote add origin heroku_git_url
#git push origin master

git push heroku master

Once app is deployed it will show you an url which you can access publicly from internet.

To see error logs

heroku logs --tail