What is React?

React is a declarative, efficient, and flexible JavaScript library for building user interfaces. It lets you compose complex UIs from small and isolated pieces of code called “components”.

Creating an App

Prerequisite

├──> Node 8.10.0 or later version installed in your system
├──> Basic knowledge of HTML, CSS and JavaScript

node --version

npm --version

Getting Started

To create a new app, you may choose one of the following methods:

npx

npx create-react-app my-app

npm

npm install -g create-react-app
create-react-app my-app

It will create a directory called my-app inside the current folder.
Inside that directory, it will generate the initial project structure and install the transitive dependencies:

my-app
├── README.md
├── node_modules
├── package.json
├── .gitignore
├── public
│   ├── favicon.ico
│   ├── index.html
│   └── manifest.json
└── src
    ├── App.css
    ├── App.js
    ├── App.test.js
    ├── index.css
    ├── index.js
    ├── logo.svg
    └── serviceWorker.js

No configuration or complicated folder structures, just the files you need to build your app.
Once the installation is done, you can open your project folder:

cd my-app

Inside the newly created project, you can run some built-in commands:

npm start

Runs the app in development mode.
Open http://localhost:3000 to view it in the browser.

The page will automatically reload if you make changes to the code.
You will see the build errors and lint warnings in the console.

npm test

Runs the test watcher in an interactive mode.
By default, runs tests related to files changed since the last commit.

npm run build

Builds the app for production to the build folder.
It correctly bundles React in production mode and optimizes the build for the best performance.

The build is minified and the filenames include the hashes.

Your app is ready to be deployed.