react js

 react js

it is library 

develope dlibrary using javascript 

free and open source

it is 

npx create-react-app my-react-app

using reactnative 

we can build mobile applicaiton

component absed architecture

each feature if we develop in component that called component based architecture

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component using this reusability

react is a virtual dom 

dom => 

and virtual dom 

html => before showing html in browser 

browser it develops in dom  

means document object model meansn in tree structiure

in parent child architecture

to increase speed

its developing in virtual dom with virtual dom it rendering the html page

to understand react have to understand javascript

basic level

arrow  and es6

after installing in terminal it shwos likethis 

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Need to install the following packages:

create-react-app@5.0.1

Ok to proceed? (y) y

npm WARN deprecated tar@2.2.2: This version of tar is no longer supported, and will not receive security updates. Please upgrade asap.

Creating a new React app in /opt/lampp/htdocs/hpanel/react/my-react-app.

Installing packages. This might take a couple of minutes.

Installing react, react-dom, and react-scripts with cra-template...

added 1494 packages in 2m

258 packages are looking for funding

run `npm fund` for details

Initialized a git repository.

Installing template dependencies using npm...

added 67 packages, and changed 1 package in 21s

262 packages are looking for funding

run `npm fund` for details

Removing template package using npm...

removed 1 package, and audited 1561 packages in 5s

262 packages are looking for funding

run `npm fund` for details

8 vulnerabilities (2 moderate, 6 high)

To address all issues (including breaking changes), run:

npm audit fix --force

Run `npm audit` for details.

Created git commit.

Success! Created my-react-app at /opt/lampp/htdocs/hpanel/react/my-react-app

Inside that directory, you can run several commands:

npm start

Starts the development server.

npm run build

Bundles the app into static files for production.

npm test

Starts the test runner.

npm run eject

Removes this tool and copies build dependencies, configuration files

and scripts into the app directory. If you do this, you can’t go back!

We suggest that you begin by typing:

cd my-react-app

npm start

Happy hacking!

writing code in javascript

let h1=document.createElement('h1');

h1.innerHTML="THIS IS REACT";

document.body.appendChild('h1);

like this dom will create in normal js

let h1=document.createElement('h1');

h1.innerHTML="THIS IS REACT";

document.body.appendChild('h1);

in react 

we will not write any code in html

<div id ="root"></div>

everything applicaiton will rednrer in root

we write only id root

react tags convert to html usingvirtal dom

==

cd my-react-app

npm start

ract dom => convert ract code to html 

src /app.js

in this html code writtein in script

import logo from './logo.svg';

import './App.css';

function App() {

return (

<div className="App">

<header className="App-header">

<img src={logo} className="App-logo" alt="logo" />

<p>

Edit <code>src/App.js</code> and save to reload.

</p>

<a

className="App-link"

href="https://reactjs.org"

target="_blank"

rel="noopener noreferrer"

>

Learn React

</a>

</header>

</div>

);

}

export default App;

==

write hte varaible using src={logo}

curly bracket

<h1 class="" id="" style="" >this is </h1>

i wanan display above h1 tag like below

let heading = React.createelement(

'h1',{class:'bg-blue'},

"this si react"

);

let element=document.getElementById('root');

let root = ReactDOM.createRoot(root);

root.render();

<div id ="root"></div>

src/index.js

import React from 'react';

import ReactDOM from 'react-dom/client';

import './index.css';

import App from './App';

import reportWebVitals from './reportWebVitals';

const root = ReactDOM.createRoot(document.getElementById('root'));

root.render(

<React.StrictMode>

<App />

</React.StrictMode>

);

test.html

we will write one html tag root

remeing all are javascript

we can write code at 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>

</head>

<body>

<div id="root"></div>

<div id="mydiv"></div>

<script src="./app.js"></script>

<script type="text/babel">

function Hello() {

return <h1>Hello World!</h1>;

}

const container = document.getElementById('mydiv');

const root = ReactDOM.createRoot(container);

root.render(<Hello />)

</script>

</body>

</html>

or call app.js 

let heading = React.createElement(

'h1', {id: 'bg-blue'}, "this is react"

);

let ele = document.getElementById('root');

let react = ReactDOM.createRoot(ele);

react.render(heading);

let heading = React.createElement(

'h1', {id: 'bg-blue'}, "this is react"

);

ist argument is tag

second one is id

thir one is text

<ul> <li> </li>

<li></li>

</ul>

create one tag

create one tag

creat one tag and call that as child 

then exponrt at end

let heading = React.createElement(

'h1', {id: 'bg-blue'}, "this is react"

);

let second = React.createElement(

'p', {id: 'sec'}, "this is second"

);

let wrapper = React.createElement(

'div', {}, [heading,second]

);

let ele = document.getElementById('root');

let react = ReactDOM.createRoot(ele);

react.render(wrapper);

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