What is React JS

React is a popular JavaScript library for building user interfaces. It allows developers to create reusable components that can be easily rendered and updated in response to changes in data or user interactions. Its main objectives are:

Component-based architecture: React allows developers to create reusable components that can be easily rendered and updated in response to changes in data or user interactions. This component-based architecture promotes modularity and code reuse, making it easier to build and maintain large-scale applications.

import React from 'react';

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

export default HelloWorld;

State management: React provides a mechanism for managing and updating the state of a component. State is a collection of data that determines the behavior and render of a component. React's setState() method allows developers to update a component's state, which triggers a re-render of the component.

import React, { useState } from 'react';

function Counter() {
  const [count, setCount] = useState(0);

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

export default Counter;

Virtual DOM: React uses a virtual DOM, which is a lightweight representation of the actual DOM (Document Object Model). When a component's state changes, React will update the virtual DOM and then make the necessary changes to the actual DOM. This improves performance compared to direct manipulation of the DOM.

Event handling: React offers a powerful mechanism for handling events, such as user interactions. In React, events are handled using event handlers, which are functions that are called in response to a specific event. Event handlers can be passed as props to a component, which can then use them to update the component's state or perform other actions.

Functional components and hooks: React introduced hooks, which allow developers to use state and other React features in functional components, rather than just class components. This makes the code more readable and easy to maintain.

In summary, React's main objectives are to provide a component-based architecture, efficient state management, a virtual DOM, powerful event handling, and functional components with hooks to make it easy to build and maintain web applications.