React

Question 1

What is Reactjs?

Answer 1

React is a JavaScript library that makes building user interfaces easy. It was developed
by Facebook.

Question 2

Does React use HTML?

Answer 2

No, It uses JSX, JavaScript XML. which is similar to HTML.

Question 3

most significant drawbacks of React

Answer 3

there is no predefined way to structure your app

Question 4

State the difference between Real DOM and Virtual DOM

Answer 4

.Real DOM Virtual DOM
It is updated slowly.It allows a direct update from HTML. It wastes too much memory.

.Virtual DOM
It updates faster.It cannot be used to update HTML
directly.Memory consumption is less

Question 5

What is Flux Concept In React?

Answer 5

Flux is a pattern for managing how data flows through a React application.
There are three distinct roles for dealing with data in the flux methodology:
Dispatcher, Stores,Views

Question 6

Define the term Redux in React

Answer 6

Redux is a library used for front end development. It is a state container for JavaScript
applications which should be used for the applications state management. You can test
and run an application developed with Redux in different environments.

Question 7

What is the ‘Store’ feature in Redux?

Answer 7

Redux has a feature called ‘Store’ which allows you to save the application’s entire State
at one place. Therefore all it’s component’s State are stored in the Store so that you will
get regular updates directly from the Store. The single state tree helps you to keep track
of changes over time and debug or inspect the application.

Question 8

What is an action in Redux?

Answer 8

Actions are plain JavaScript object that contains information.
. The action-type and the action data are always stored in the action object.

Question 9

When was React first released?

Answer 9

React was first released on March 2013.

Question 10

Name the important features of React

Answer 10

Virtual Dom
single page applications
SEO friendly with ssr
JSX
Component Driven

Question 11

Explain the term stateless components

Answer 11

Stateless components are pure functions that render DOM-based solely on the
properties provided to them.

Question 12

What is dispatcher?

Answer 12

A dispatcher is a central hub of app where you will receive actions and broadcast
payload to registered callbacks.

Question 13

What is meant by callback function? What is its purpose?

Answer 13

A callback function should be called when setState has finished, and the component is
retendered. As the setState is asynchronous, which is why it takes in a second callback
function.

Question 14

Explain the term high order component

Answer 14

A higher-order component also shortly known as HOC is an advanced technique for
reusing component logic. It is not a part of the React API, but they are a pattern which
emerges from React’s compositional nature.

Question 15

What are Props in react js?

Answer 15

Props mean properties, which is a way of passing data from parent to child. We can say
that props are just a communication channel between components. It is always moving
from parent to child component.

Question 16

Name two types of React component

Answer 16

Two types of react Components are:
Function component
Class component

Question 17

synthetic event in React js

Answer 17

Synthetic event is a kind of object which acts as a cross-browser wrapper around the
browser’s native event. It also helps us to combine the behaviors of various browser into
signal API.

Question 18

What is React State?

Answer 18

The state is a built-in React object that is used to contain data or information about the component. A component’s state can change over time; whenever it changes, the component re-renders.

Question 19

Explain the use of ‘key’ in react list

Answer 19

Keys allow you to provide each list element with a stable identity. The keys should be
unique.

Question 20

Explain error boundaries?

Answer 20

Only class components can be error boundaries.
Error boundaries are React components that catch JavaScript errors anywhere in their child component tree, log those errors, and display a fallback UI instead of the component tree that crashed. Error boundaries catch errors during rendering, in lifecycle methods, and in constructors of the whole tree below them.

Question 21

Explain strict mode

Answer 21

StrictMode allows you to run checks and warnings for react components. It runs only on
development build. It helps you to highlight the issues without rendering any visible UI.

Question 22

What is portal in React with example?

Answer 22

Portals provide a first-class way to render children into a DOM node that exists outside the DOM hierarchy of the parent component.

Question 23

What is Context?

Answer 23

React context helps you to pass data using the tree of react components. It helps you to
share data globally between various react components.

Question 24

What is the use of Webpack?

Answer 24

Webpack in basically is a module builder. It is mainly runs during the development
process.

Question 25

What is Babel in React js?

Answer 25

Babel, is a JavaScript compiler that converts latest JavaScript like ES6, ES7 into plain
old ES5 JavaScript that most browsers understand.

Question 26

How can a browser read JSX file?

Answer 26

If you want the browser to read JSX, then that JSX file should be replaced using a JSX
transformer like Babel and then send back to the browser.

Question 27

Can you update props in react?

Answer 27

You can’t update props in react js because props are read-only. Moreover, you can not
modify props received from parent to child.

Question 28

Can you update the values of props?

Answer 28

It is not possible to update the value of props as it is immutable.