Core Concepts of React Js

React is a JavaScript library for building user interfaces. It is designed to make building web applications with complex UI easier and more efficient. Here are some core concepts of React that you should understand:

Components: In React, a component is a self-contained piece of code that represents a part of a UI. A component can accept input (called “props”) and return a JSX template that describes how the component should be rendered.

JSX: JSX is a syntax extension for JavaScript that allows you to write HTML-like code in your JavaScript files. When a JSX element is rendered, it is transformed into regular JavaScript function calls.

State: In React, a state is an object that represents the data for a component. A component’s state can be modified by calling setState, which will trigger a re-render of the component.

Props: Props are data that is passed from a parent component to a child component. Props are read-only and cannot be modified within the child component.

Lifecycle methods: React components have a lifecycle that consists of several stages, such as mounting, updating, and unmounting. You can use lifecycle methods to perform certain actions at different stages of a component’s lifecycle.

Virtual DOM: React uses a virtual DOM (Document Object Model) to improve performance by minimizing the number of DOM manipulations required when rendering components. When a component’s state or props change, React compares the new virtual DOM with the previous virtual DOM and determines the minimum number of changes needed to update the actual DOM.

For example, let’s say you have a BlogPost component that displays the title and body of a blog post. When the title or body is updated, the BlogPost component will re-render itself using the new data. Instead of updating the entire DOM, React will compare the virtual DOM representation of the BlogPost component before and after the update, and only update the parts of the actual DOM that have changed.

Event handling: In React, you can handle events such as clicks or form submissions using event handlers. Event handlers are functions that are called in response to a specific event.

For example, let’s say you have a LikeButton component that displays a button that a user can click to like a post. You can add an event handler to the button to handle the click event:

import React from 'react';

function LikeButton(props) {
  const handleClick = () => {
    // Increment the like count

  return (
    <button onClick={handleClick}>
      Like ({props.likeCount})

export default LikeButton;

In this example, the LikeButton component has a handleClick function that is called when the button is clicked. The handleClick function increments the like count by calling the onLike prop, which is passed down from the parent component.

I hope these examples help! Let me know if you have any questions.