Reactjs Interview Questions And Answers For Beginners

Looking for a job that requires you to have an understanding of React.Js? Or are you trying to hire candidates who are well-versed in React.Js? You are in the right place. As a candidate for React.Js developer jobs or as a pro recruiter, you may find this cautiously curated listing of React.Js interview questions and solutions for beginners handy. We hope that the time you spend on this page will take you a step closer to your dream job or your dream candidate.

Interview questions and answers on Reactjs for beginners

Interview questions and answers; Source: GeeksforGeeks

What is React?

It is an open-source front-end JavaScript library most popular for single-web page web programs. It is beneficial when interactive and complicated UIs are constructed for websites or mobile apps. React.Js was released for use in 2015, and in view of that, it has become one of the most relied-on and used technologies of recent times. It has developed one of the largest developer communities around itself.

List some of React.Js’ features.

Important features of React.Js include:

  • Instead of a real DOM, there's a Virtual DOM
  • It fully renders the HTML files at the server into client HTML pages; in other words, server-side rendering
  • In React.Js, the data may be passed to the alternative components of an application in only one way. In other words, there is a unidirectional flow of data.

What are the main benefits of React.js?

The predominant benefits of React.Js are:

  • It complements the overall performance of the application
  • It may be used from the client side as well as the server side
  • It is easier to read code in React.Js because of JSX
  • It offers simple integration with frameworks consisting of Angular, Meteor, etc.
  • It is straightforward to write UI test cases with React.Js

If you can provide some practical experience demonstrating the advantages of React.Js on this React.Js interview question, you're probably going to impress the recruiter.

What is JSX?

JSX is the syntax extension for Javascript in React.Js. With the assistance of JSX, it is simple to outline how the user interface will appear. Additionally, with JSX, the file containing the Javascript code may be used to write the HTML structures as well.

Describe an events in React.Js.

When a user presses a key, clicks the mouse, or performs any action on the machine, or when the machine itself triggers an action, these actions are registered as events in React.Js.

  • In React.Js, we use camelCase to call events, unlike in HTML, where we use the lowercase
  • In React.Js, due to JSX, a function is passed as an event handler in place of the string in HTML

How do lists work in React.js?

Lists in React.Js are created similarly to how they may be created in regular Javascript. With lists, data may be displayed in an orderly way, which is beneficial for showing menus on websites. For traversing lists, the map() function is used. For instance,

  • An array of numbers is taken by way of the map() function and their value is expanded through five
  • var numbers = [2, 4, 6, 8, 10]
  • const multiplyNums = numbers.Map((wide variety =>  return (range*five); );
  • console.Log (multiplyNums);

Output: The output in Javascript will be logged inside the console. The output inside the above case is [10, 20, 30, 40, 50]

Why are keys used in React.Js lists?

Keys are utilized in React.Js Lists because:

  • Key enables figuring out what items were altered, moved, or deleted from lists
  • With the help of keys, it's far easier to determine which objects need to be re-rendered, in preference to all additives being re-rendered all the time.

React.Js interview questions that ask about the use of a certain feature or component in React.Js programming are not unusual.

Is HTML used in React?

No, it uses an HTML-in-JavaScript syntax called JSX (JavaScript and XML) that converts HTML tags to React elements.

What is the release date of React?

March 2013.

Can you say two downsides of React?

It is difficult to combine with an MVC framework like Rails. Also, it can take time to understand the use of hooks and references correctly.

Can you define the differences between Real DOM and Virtual DOM?

Real DOM and Virtual DOM are different in the following ways:

Virtual DOM

Real DOM

Updates faster

Updates slower

No memory wastage

Excess memory wastage

Can't update HTML directly

Update HTML directly

DOM manipulation is easy

DOM manipulation is costly

Explain the Flux Concept in React.

It is a brand new type of structure used for client-side internet programs. Supports the concept of Unidirectional Data Flow.

What is Redux in React?

An open-source JavaScript library for front-end development acts as a container for JavaScript applications; this is used for application state management.

Explain the ‘Store’ feature.

It is a function of Redux that lets the software keep the whole State in one vicinity. This permits you to get everyday updates from the shop immediately.

What is a high-order component in React?

It is an advanced-level method in React for reusing component logic.

What is the presentational phase?

It is part of React that just renders HTML, and its function is presentation markup.

Explain Props in ReactJS.

Props in React mean properties. They act as a communication exchange channel from parent to child.

What does the super keyword mean in React?

It is used to call super or parent class.

What is a yield catchphrase in JavaScript?

It is used to pause and resume a generator work.

List the two forms of the React component.

Two varieties of React components are as follows:

  • Function component
  • Class component

What is an synthetic event in ReactJS?

It is an object that serves as a browser wrapper for the browser’s native event.

In Redux, what is an action?

In Redux, an action is an object that includes information about an event that has taken place in an application.

What are stateless components?

They are pure functions without a rendering method.

What is a React Router?

It is a library for routing in React.

Can you list a few animation packages in React?

Some animation packages are as follows:

  • Framer Motion
  • React Transition Group
  • React Move

Explain Jest.

Jest is a JavaScript framework created by Facebook and is based totally on Jasmine. Its function-wealthy feature-rich API facilitates getting outcomes faster.

What is the dispatcher?

It is the central hub of data flow in Flux software that acts as a directory of callbacks.

Explain the callback feature.

It is called when setState() has been completed. A state may be updated in response to prop modifications or server responses using the setState() method. The principal purpose is to stop a component from re-rendering.

Explain React State.

It is an object that stores the aspect’s property values. Also, it decides how the component renders and behaves.

Can you update a state in ReactJS?

Yes, it is able to be updated directly or indirectly. To enforce this, you'll use either this.SetState characteristic, or the updater function.

What is the use of the arrow feature in React?

The arrow feature helps to create a compact function expression. Also, they help to predict bugs while being passed as a callback.

List the lifecycle steps of React.

The steps are as follows:

  • Initialization
  • State/Property updates
  • Destruction

What are React portals?

They are used to render an element out of its hierarchy using CreatePortalmethod. Hence, they permit developers to render the hierarchy tree outside.

Explain Context.

React Context is a way to share data globally between React components. It accomplished this by passing props from parent to child and storing them in a store. Thus, child component(s) can use those props via the store.

What is the use of Webpack?

Webpack is a command-line tool used to package various code files and assets into a single large file. It has been constructed over Node.Js and enables minimization in Javascript, CSS files, images, and so on.

What is Babel?

It is an open-source JavaScript compiler that converts modern JavaScript versions to old ones.

How are ReactJS and React Native different?

Where ReactJS is a front-end open-source JavaScript library for UIs, React Native is an open-source mobile framework for platforms such as Android and iOS.


React.js interview questions; Source: Masai School

With the above listing, we have attempted to give a few trending ReactJS interview questions that not only help scrutinize the proper candidate but also help contenders crack the proper interview. With this exhaustive listing, we've attempted to cover most, if not all, of the beginner-level Reactjs interview questions and solutions.

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