TOP 50 React JS Interview Question and Answer by Shiva Sir |  React JS Interview Question and Answer: Now a days most of the IT Company asked REACT JS Question mostly in interview. I am creating this article to provide help to all REACT IMPORTANT QUESTIONS  I am Shiva Gautam,  I have 15 Years of experience in Multiple IT Technology, I am Founder of Shiva Concept Solution Best Programming Institute with 100% Job placement guarantee. If you want to know more visit  Shiva Concept Solution                                  Watch Complete Video Visit  Youtube Shiva Concept Top 50 React Interview Questions and Answers React is one of the most popular JavaScript libraries for building user interfaces. If you're preparing for a React job interview or simply want to sharpen your skills, this comprehensive list of 50 important React interview questions will help you master the key ...

ReactJS is a declarative, efficient, and flexible JavaScript library for building reusable UI components.  It is an open-source, component-based front-end library responsible only for the view layer of the application.  It was created by Jordan Walke , who was a software engineer at Facebook.  It was initially developed and maintained by Facebook and was later used in its products like WhatsApp & Instagram.  Facebook developed ReactJS in 2011 in its newsfeed section, but it was released to the public in the month of May 2013. Today, most of websites are built using MVC (model view controller) architecture.  In MVC architecture, React is the 'V' which stands for view, whereas the architecture is provided by the Redux or Flux . A ReactJS application is made up of multiple components, each component responsible for outputting a small, reusable piece of HTML code.   The components are the heart of all React applications . These components can be nested wit...

  Program of React-JS to check prime number using constant object? import React from "react"; export class Prime extends React.Component {     state = {         num: 9,         i: 2,         s:null       };        constructor()    {         super();        }    render()    {     const { num } = this.state;     for(this.state.i=2;this.state.i<num;this.state.i++)     {         if(num%this.state.i==0)         {             this.state.s = "not prime";             break;         }     }     if(num==this.state.i)     {         this.state.s = "prime";     }     return(        ...

  Uncontrolled form input in React-JS? If we want to take input from users without any separate event handling then we can uncontrolled the data binding technique. The uncontrolled input is similar to the traditional HTML form inputs. The DOM itself handles the form data. Here, the HTML elements maintain their own state that will be updated when the input value changes. To write an uncontrolled component, you need to use a ref to get form values from the DOM. In other words, there is no need to write an event handler for every state update. You can use a ref to access the input field value of the form from the DOM. Example of Uncontrolled Form Input:- import React from "react" ; export class Info extends React . Component {     constructor ( props )     {         super ( props );         this . fun = this . fun . bind ( this ); //event method binding         this . input = React . createRef ();...

Controlled components have functions that govern the data passing into them on every onChange event, rather than grabbing the data only once, e.g., when you click a submit button. This data is then saved to the state and updated with setState() method. This makes components have better control over the form elements and data. A controlled component takes its current value through props and notifies the changes through events or callbacks like an onChange event. A parent component "controls" these changes by handling the callback and managing its own state and then passing the new values as props to the controlled component. It is also called a "dumb component." Code of Controlled Component in React JS:- Now i am implementing addition program to implement react-js controlled component. import   React , {  Component  }  from   'react' ;   export   class   Controlledcomponent   extends   React . Component {    ...