npm install react react-redux @reduxjs/toolkit

main.jsx

import { StrictMode } from 'react'
import { createRoot } from 'react-dom/client'
import './index.css'
import App from './App.jsx'
import { Provider } from 'react-redux'
import store from './store.js'

createRoot(document.getElementById('root')).render(
  <StrictMode>
    <Provider store={store}> {/* Wrap your App inside Provider */}
    <App />
    </Provider>
  </StrictMode>,
)

store.jsx

import { configureStore } from "@reduxjs/toolkit";

const initialState = { count: 0 };

const counterReducer = (state = initialState, action) => {
  switch (action.type) {
    case "INCREMENT":
      return { count: state.count + 1 };
    case "DECREMENT":
      return { count: state.count - 1 };
    default:
      return state;
  }
};

const store = configureStore({
  reducer: counterReducer,
});

export default store;

App.jsx

import { useSelector, useDispatch } from "react-redux";

function App() {
  const count = useSelector(state => state.count); // Get state from Redux store
  const dispatch = useDispatch(); // Get dispatch function

  return (
    <>
      <button onClick={() => dispatch({ type: "INCREMENT" })}>+</button>
      <button onClick={() => dispatch({ type: "DECREMENT" })}>-</button>
      <h1>{count}</h1>
    </>
  );
}

export default App;

---

src/store.js

import { combineReducers, configureStore } from "@reduxjs/toolkit";

const initial_state = { userid: 1, emailid: "admin@nstest.com" }

const adminreducer = (state = initial_state, {type, payload}) => {

  if(type == "SET_VAL") {
    console.log("INSIDE SET_VAL case")
    return {...state, emailid : payload.emailid }
  }

  return state
}

const userreducer = (state = { payload: {} }, {type, payload}) => {

    if(type == "SET_USER_VAL") {
      console.log("INSIDE SET_USER_VAL case")
      return {...state, payload : payload }
    }
  
    return state
  }


const reducer = combineReducers({adminreducer, userreducer})

const store = configureStore({reducer})

export default store;

src/index.js

import React from 'react';
import ReactDOM from 'react-dom/client';
import './index.css';
import App from './App';
import reportWebVitals from './reportWebVitals';
import store from './store';
import { Provider } from 'react-redux';

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
  <React.StrictMode>
    <Provider store={store}>
    <App />
    </Provider>
  </React.StrictMode>
);

reportWebVitals();

src/App.js

import { useEffect } from "react";
import { useDispatch, useSelector } from "react-redux";
import { BrowserRouter, Route, Routes } from "react-router-dom";
import Admin from "./components/Admin";
import Contact from "./components/Contact";
import Home from "./components/Home";
import Layout from "./components/Layout";
import User from "./components/User";

function App() {

  const mystate = useSelector((state) => state)

  return (
    <div>
      This is app component <br />
      {mystate.payload}
      <Contact />
      <BrowserRouter>
        <Routes>
          <Route path="/" element={ <Layout />}>

            <Route index element={ <Home /> } />
            <Route path="admin" element={ <Admin /> } />
            <Route path="user" element={ <User /> } />

          </Route>
        </Routes>
      </BrowserRouter>
    </div>
  );
}

export default App;

src/components/Admin.js

import React, { useEffect } from 'react'
import { useDispatch } from 'react-redux'

export default function Admin() {

    const dispatch = useDispatch()

    useEffect(() => {
        console.log("Hello dispatcher...")
        dispatch({ type : "SET_VAL", payload: { "emailid" : "admin@devtest.com"} })
    }, [])

  return (
    <div>Admin</div>
  )
}

src/component/User.js

import React, { useEffect } from 'react'
import { useDispatch } from 'react-redux'

export default function User() {

    const dispatcher = useDispatch()

    useEffect(() => {
        console.log("Inside user use effect")

        dispatcher({ 
          "type" : "SET_USER_VAL", 
          payload : { emailid : "user@devtest.com", time: new Date().toJSON().slice(0, 10) }
        })

    }, [])

  return (
    <div>User</div>
  )
}

Setter and Getter for Redux

store.js

import { combineReducers, configureStore } from "@reduxjs/toolkit";

const appdata = (state = {}, {type, payload}) => {

  if(type == "SET_APP_DATA") {
    return {...state, [payload[0]]: payload[1] }
  }

  if(type == "DELETE_APP_DATA") {
    return {...state, [payload]: undefined }
  }

  return state
}

const reducer = combineReducers({appdata})
const store = configureStore({reducer})

export const setRedux = (key, val) => {
  store.dispatch({ type : "SET_APP_DATA", "payload": [key, val] })
}

export const getRedux = (key = undefined) => {
  return store.getState().appdata[key]
}

export const removeRedux = (key = undefined) => {
  store.dispatch({ type : "DELETE_APP_DATA", "payload": key })
}


export default store;

In component

setRedux("username", "admin")
setRedux("email", "admin@nstest.com")
setRedux("phoneno", "9876543210")

getRedux("email")
getRedux("name")

removeRedux("email")

listing.html

<!-- https://datatables.net/examples/server_side/simple.html -->
<!-- https://datatables.net/manual/ajax -->
<!-- https://datatables.net/manual/ajax#Column-data-points -->
<!-- https://stackoverflow.com/questions/64526856/how-to-add-edit-delete-buttons-in-each-row-of-datatable -->

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" type="text/css" href="https://cdn.datatables.net/1.12.1/css/jquery.dataTables.css">
  
    <link rel="stylesheet" type="text/css" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/5.2.0/css/bootstrap.min.css">
    <link rel="stylesheet" type="text/css" href="https://cdn.datatables.net/1.12.1/css/dataTables.bootstrap5.min.css">

    <script type="text/javascript" charset="utf8" src="https://code.jquery.com/jquery-3.6.1.js"></script>
<script type="text/javascript" charset="utf8" src="https://cdn.datatables.net/1.12.1/js/jquery.dataTables.js"></script>
    <title>Document</title>
</head>
<body>
<table id="example" class="display table table-striped" style="width:100%">
        <thead>
            <tr>
                <th>Name</th>
                <th>Address</th>
                <th>Salary</th>
                <th>Action</th>
            </tr>
        </thead>
    </table>
</body>
<script>
    $(document).ready(function () {
    $('#example').DataTable({
        processing: true,
        serverSide: true,
        ajax: 'http://ciacloud.in/juhi/rems/get_employees.php',
        columns: [
            { data: 'name'},
            { data: 'address'},
            { data: 'salary'},
            { 
                data: 'id',
                render: (data,type,row) => {
                    console.log({data,type,row})
                   return `<a href='edit_form.php?id=${data}'>Edit</a> | <a href='delete.php?id=${data}'>Delete</a>`;
                 }
            }
        ],
        columnDefs: [
            { orderable: false, targets: -1 },
            {
                "defaultContent": "-",
                "targets": "_all"
            }],
            order: [0,1,2,3],
    });
});
</script>
</html>

get_employees.php

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database";

$params = $_REQUEST;
header('Access-Control-Allow-Origin: *');

$search = isset($params['search']['value'])  && $params['search']['value'] != '' ? $params['search']['value'] : '';

try {
  $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
  $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

  $where = '';

  if($search !== '')
	  $where = " name LIKE '$search%' ";
  else
	  $where = " 1 = 1 ";

  $sort_columns = ['name', 'address', 'salary'];
  $sort_column_index = $params['order'][0]['column'];
  $sort_order = isset($params['order'][0]['dir']) && $params['order'][0]['dir'] != 1 ? $params['order'][0]['dir'] : 'desc';

  $order_by = " $sort_columns[$sort_column_index] $sort_order";
	
  $offset = $params['start'];
  $limit = $params['length'];

  $sql = "SELECT * FROM employees WHERE $where ORDER BY $order_by LIMIT $offset, $limit";
  $stmt = $conn->prepare($sql);
  $stmt->execute();

  // set the resulting array to associative
  $result = $stmt->setFetchMode(PDO::FETCH_ASSOC);
  $employees = $stmt->fetchAll();

} catch(PDOException $e) {
  echo "Error: " . $e->getMessage();
}

$count_sql = "SELECT COUNT(*) FROM employees WHERE $where";
$result = $conn->prepare($count_sql); 
$result->execute(); 
$totalRecords = $result->fetchColumn(); 

$conn = null;


$json_data = array(
		"draw"            => intval( $params['draw'] ),
		"recordsTotal"    => intval( $totalRecords ),
		"recordsFiltered" => intval($totalRecords),
		"data"            => $employees,
		"count_sql"	=> $count_sql,
		"sql"		=> $sql,
	);

echo json_encode($json_data);

React is a free and open-source front-end JavaScript library for building user interfaces based on UI components. It is maintained by Meta and a community of individual developers and companies. React can be used as a base in the development of single-page or mobile applications.

Create new react project

npm -v

npm i npx

npx create-react-app my-react-app

cd my-react-app
code .

Run from terminal

npm start

OR

npm start --port 8000

Open Browser and run the react app http://localhost:3000 OR http://ipaddress:3000

• 

App.js

import logo from './logo.svg';
import './App.css';

function App() {
  return (
    <>
      <h1>Test App</h1>
    </>
  );
}

export default App;

Create new component and use click and change event

src/components/Add.js

import { Fragment, useState } from "react";


function Add () {

    const [ num1, setNum1 ] = useState(0);
    const [ num2, setNum2 ] = useState(0);
    const [ result, setResult ] = useState(0);

    function addFun() {
        setResult(num1 + num2);
    }

    return (<Fragment>
        <h1>Addition of two numbers</h1>
        <input type="text" onChange={ e => setNum1(parseInt(e.target.value)) }/>
        <input type="text" onChange={ e => setNum2(parseInt(e.target.value)) } />
        <button onClick={addFun}>Get Addtion</button>
        <div>{result}</div>
    </Fragment>);
}

export default Add;

Add this Add component in App component as tag <Add />

import './App.css';
import Add from './components/Add';

function App() {
  return (
    <>
      <Add />
      <Add />
      <h1>Test App</h1>
    </>
  );
}

export default App;

React Properties

App.js

import './App.css';
import Add from './components/Add';

function App() {
  return (
    <>
      <Add x="5" y="6"/>
      <Add x="7" y="8"/>
      <h1>Test App</h1>
    </>
  );
}

export default App;

Add.js

import { Fragment, useState } from "react";


function Add (props) {

    const [ num1, setNum1 ] = useState(parseInt(props.x));
    const [ num2, setNum2 ] = useState(parseInt(props.y));
    const [ result, setResult ] = useState(0);

    function addFun() {
        setResult(num1 + num2);
    }

    return (<Fragment>
        <h1>Addition of two numbers</h1>
        <input type="text" onChange={ e => setNum1(parseInt(e.target.value)) }/>
        <input type="text" onChange={ e => setNum2(parseInt(e.target.value)) } />
        <button onClick={addFun}>Get Addtion</button>
        <div>{result}</div>
    </Fragment>);
}

export default Add;

Ajax call in React.js

Create new component Users

components/User.js

import { Fragment } from "react";

function User(props) {

    //object destructoring assignment
    const {id, name, username, email} = props.user;

    return (
        <Fragment>
            <tr>
                <td>{props.user.id}</td> 
                <td>{props.user.name}</td>
                <td>{username}</td>  
                <td>{email}</td>
            </tr>
        </Fragment>
    );

}

export default User;

components/UsersListing.js

import { Fragment, useState } from "react";
import User from "./User";

function UsersListing () {

    const [ users, setUsers ] = useState([]);


    function getUsers() {

        fetch("https://jsonplaceholder.typicode.com/users")
        .then(response => response.json())
        .then(json => {
                console.table(json)
                var rows = [];
                for(let i = 0; i < json.length; i++) {
                    rows.push(<User key={i} user={json[i]}/>);
                }
                setUsers(rows);
            }
        );

    }

    return (<Fragment>
        <h1>Users Listing</h1>
        
        <button onClick={getUsers}>Get Users</button>

        <table border='1'>
            <thead>
                <th>Id</th>
                <th>Name</th>
                <th>Username</th>
                <th>Email</th>
            </thead>
            <tbody>
                {users}
            </tbody>
        </table>
    </Fragment>);
}

export default UsersListing;

Use <UsersListing /> component in App.js JSX to show users list

Routing

https://www.w3schools.com/REACT/react_router.asp

Deploy React App on Github

Create repository on github

git init
git add .
git commit -m "first commit"
git branch -M main
git remote add origin https://github.com/<username>/<repositoryname>.git

git remote set-url origin https://<githubtoken>@github.com/<username>/<repositoryname>.git
#git clone https://<username>:<githubtoken>@github.com/<username>/<repositoryname>.git

To get github token Go To Profile Settings => Developer Settings => Personal Access Token => Generate New Token

npm install gh-pages --save-dev

vim package.json

{
  "name": "my-app",
  "version": "0.1.0",
  "homepage": "https://gitname.github.io/repositoryname",
  "private": true,
  
  
 "scripts": {
    "predeploy": "npm run build",
    "deploy": "gh-pages -d build",
    "start": "react-scripts start",
    "build": "react-scripts build",

npm run deploy

git status
git add .
git commit -m 'deploy react on github'
git push

https://<username>.github.io/<repositoryname>/

To publish react app locally

npm run build

verify build directory and index.html file

build index.html

<link rel="manifest" href="manifest.json"/>
<title>React App</title>
<script defer="defer" src="./static/js/main.<yourhash>.js"></script>
<link href="./static/css/main.<yourhash>.css" rel="stylesheet">

You can publish this in xampp htdocs folder

index.html

<!DOCTYPE html>
<html>

<head>
    <script src="https://unpkg.com/react@18/umd/react.development.js" crossorigin></script>
    <script src="https://unpkg.com/react-dom@18/umd/react-dom.development.js" crossorigin></script>
    <script src="https://unpkg.com/@babel/standalone/babel.min.js"></script>
    <script src="https://unpkg.com/react-router@5.0.0/umd/react-router.min.js"></script>
    <script src="https://unpkg.com/react-router-dom@5.0.0/umd/react-router-dom.min.js"></script>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.2.1/dist/css/bootstrap.min.css" rel="stylesheet"
        integrity="sha384-iYQeCzEYFbKjA/T2uDLTpkwGzCiq6soy8tYaI1GyVh/UjpbCx/TYkiZhlZB6+fzT" crossorigin="anonymous">
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.2.1/dist/js/bootstrap.bundle.min.js"
        integrity="sha384-u1OknCvxWvY5kfmNBILK2hRnQC3Pr17a+RTT6rIHI7NnikvbZlHgTPOOmMi466C8"
        crossorigin="anonymous"></script>
</head>

<body class="container-fluid">


    <div id="root"></div>
    <script type="text/babel">

        function Home() {
            return <h1>This is home</h1>
        }

        function UserComponent() {
            return <h1>This is user</h1>
        }

        function AdminComponent() {
            return <h1>This is admin</h1>
        }


        const Router = window.ReactRouterDOM.BrowserRouter;
        const Route = window.ReactRouterDOM.Route;
        const Link = window.ReactRouterDOM.Link;
        const Prompt = window.ReactRouterDOM.Prompt;
        const Switch = window.ReactRouterDOM.Switch;
        const Redirect = window.ReactRouterDOM.Redirect;

        function App() {
            return <>
            <Router>

                <nav>
                    <ul>
                        <li>
                            <Link to="/">Home</Link>
                        </li>
                        <li>
                            <Link to="/admin">Admin</Link>
                        </li>
                        <li>
                            <Link to="/user">Users</Link>
                        </li>
                    </ul>
                </nav>

                <Switch>
                    <Route path='/user' component={UserComponent} />
                    <Route path='/admin' component={AdminComponent} />
                    <Route exact path='/' component={Home} />
                </Switch>
            </Router>
            </>;
        }

        ReactDOM.render(<App />, document.getElementById('root'))
    </script>

</body>
</html>

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

chat_server.js

const express = require('express');
const http = require('http');
const WebSocket = require('ws');

const port = 8989;
const server = http.createServer(express);
const wss = new WebSocket.Server({ server })

wss.on('connection', function connection(ws) {
  ws.on('message', function incoming(data) {
    wss.clients.forEach(function each(client) {
      if (client !== ws && client.readyState === WebSocket.OPEN) {
        client.send(data);
      }
    })
  })
})

server.listen(port, function() {
  console.log(`Server is listening on ${port}!`)
})

index.html

<center><h1>WS Chat App</h1></center>
<pre id="messages" style="height: 400px; overflow: scroll"></pre>
<input type="text" id="messageBox" placeholder="Type your message here" style="display: block; width: 100%; margin-bottom: 10px; padding: 10px;" onkeyup="validateInput(event)"/>
<button id="send" title="Send Message!" style="width: 100%; height: 30px;">Send Message</button>

<script>
  (function() {
    const sendBtn = document.querySelector('#send');
    const messages = document.querySelector('#messages');
    const messageBox = document.querySelector('#messageBox');

    let ws;

    function showMessage(message) {
      if (message instanceof Blob) {
        reader = new FileReader();

        reader.onload = () => {
        //   console.log("Result: " + reader.result);
          messages.textContent += `\n\n${reader.result}`;
        };

        reader.readAsText(message);
      } else {
        console.log("Result: " + message);
        messages.textContent += `\n\n${message}`;
      }

      messages.scrollTop = messages.scrollHeight;
      messageBox.value = "";
    }

    function init() {
      if (ws) {
        ws.onerror = ws.onopen = ws.onclose = null;
        ws.close();
      }

      ws = new WebSocket('ws://localhost:8989');
      ws.onopen = () => {
        console.log('Connection opened!');
      }
      ws.onmessage = ({ data }) => showMessage(data);
      ws.onclose = function() {
        ws = null;
      }
    }

	
    sendBtn.onclick = function() {
      if (!ws) {
        showMessage("No WebSocket connection :(");
        return ;
      }

      ws.send(messageBox.value);
      showMessage(messageBox.value);
    }
	
	
	messageBox.onkeyup = function() {
		if(event.keyCode  == 13) {
			if (!ws) {
				showMessage("No WebSocket connection :(");
				return ;
			}

			ws.send(messageBox.value);
			showMessage(messageBox.value);
		}
    }

    init();
  })();
</script>