React js

React.js is a JavaScript library for building user interfaces, particularly for single-page applications where you need dynamic, responsive, and interactive user interfaces. Developed and maintained by Facebook, React has gained widespread adoption in the web development community due to its component-based architecture and the ability to efficiently update the user interface.

Key Concepts in React.js:

  1. Components:
  • React applications are built using components, which are reusable and independent pieces of user interface.
  • Components can be class components or functional components, and they can maintain their own state and lifecycle methods.
  1. JSX (JavaScript XML):
  • React uses JSX, a syntax extension for JavaScript, to describe what the UI should look like.
  • JSX allows you to write HTML-like code in your JavaScript files, making it easier to visualize and understand the structure of your components.
  1. Virtual DOM:
  • React uses a virtual DOM to improve performance. Instead of directly manipulating the actual DOM, React updates a virtual representation and then efficiently updates the real DOM only where necessary.
  1. State and Props:
  • Components can have state, which is data that can change over time. When the state changes, React re-renders the component.
  • Props (short for properties) are used to pass data from a parent component to a child component.
  1. Lifecycle Methods:
  • Class components have lifecycle methods that are called at different stages of a component’s life, such as componentDidMount (called after the component is rendered) and componentWillUnmount (called before the component is removed).
  1. Hooks:
  • Hooks are functions that let you use state and other React features in functional components. The useState and useEffect hooks are commonly used for managing state and side effects.

Example React Component:

import React, { useState, useEffect } from 'react';

const MyComponent = () => {
  // State using the useState hook
  const [count, setCount] = useState(0);

  // Effect using the useEffect hook
  useEffect(() => {
    document.title = `Count: ${count}`;
  }, [count]);

  return (
      <p>Count: {count}</p>
      <button onClick={() => setCount(count + 1)}>Increment</button>

export default MyComponent;

In this example:

  • The component uses the useState hook to manage the count state.
  • The useEffect hook updates the document title whenever the count changes.
  • JSX is used to define the component’s UI.

React provides a powerful and efficient way to build modern web applications, and it’s often used in conjunction with other libraries and tools such as React Router for navigation, Redux for state management, and webpack for bundling.

React is a popular library of javascript used to create Interface. React js is created by Jordan Walke under Facebook. the idea behind creating React js was big data-driven for the Facebook website.

React js is used to create one page-based website through reusable UI(user interface). initially React js project was viewed with some doubt due to its convention. in modern times React js is quite popular to make single-page-based web development.

React js developers community has grown to a big scale due to its flexibility and reusable UI. React js was originally used for Facebook social feed

Why should we learn React js?

We know that React js is created under Facebook to drive big data on Facebook for social feeds. it means if we want a flexible website that can drive big data then we should choose React js. React js create virtual DOM before doing any changes to the browser DOM.

React js virtual DOM does all necessary changes before going to manipulate browser DOM which means React does only changes in browser DOM that we needed through reusable UI. React js is very popular in the developer community so through that we can solve any big problems that we will face while developing any React project.

React js is a small library of javascript through that we can make a single-based user interface that will behave like a web app. In modern times we know that the popularity of web apps is growing very fast so through React js we can easily create a web app that will be fast and more flexible to use that website and will show a great user interface

we know that through React we can create a web app or app for any platform like Android or IOS it means we don’t need to learn more native programming language for many different platforms to make native app. just write once and use everywhere

we know that through React js development speed will be very fast with high scalability. React js is used by many big companies like Facebook, Twitter, Yahoo, Netflix, Microsoft, and many more

Hello world programme in React js

import React from 'react';
import ReactDOM from 'react-dom';

class Test extends React.Component {
render() {
return <h1>Hello World!</h1>;

ReactDOM.render(<Test />, document.getElementById('root'));

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