Take The Quiz! Top 20 React.js Interview Questions

12 August 2021

A Guide to Answering the Most Important React.JS Developer Interview Questions

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Question #1. What are the major advantages of React.JS?

Answer #1
· SEO-friendliness,
· Virtual DOM,
· reusable components
· and one-way data flow

You are correct! All of these advantages are pivotal to ReactJS:
· Being SEO-friendly allows your project to show better organic search results in order to attract users and drive business goals;
· One-way data flow allows for a simpler and more stable code, as in React.JS’ structure parent data cannot be affected by any changes made to child elements;
· React.JS isolates each and every component, which, in turn, means that all the components of the code are perfectly reusable and will not affect all the copies of that component if any changes are made to it;
· And last but not least, React uses Virtual DOM. If any changes are made, it does not rewrite the entire DOM tree and updates the manipulated element. As a result, it renders React.JS’ Virtual DOM much more efficient and faster performing.

Answer #2
· Being maintained by Google,
· Two-way data binding
· Usage of TypeScript

Take a deep breath and let the stress go, as you seem somewhat confused. Easiness to learn and virtual DOM are React.JS’ advantages, whilst usage of TypeScript and two-way data binding are Angular’s. You are near the right track, but be more attentive to the next question!

Question #2. What are the main features of React.JS you would like to list?

Answer #1
MVC Architecture, Less Code Framework, Dependency Injection, Directives

While all of these features are worth writing home about, they are the main features of Angular. And, also, some type of Dependency Injection is possible in React.JS, it is far from being a feature and requires lots and lots of tinkering around.

Answer #2
JSX, Event Handling, Virtual DOM, Computed Properties, Template

Answer #2
You are close, but no cigar on this one, as this answer is, in fact, a mix of Vue.JS’ and React.JS’ main features. Let’s clear the smog a little: both Vue.JS and React.JS use virtual DOM and to great result, we might add, but where the first uses Templates, the second goes with JSX. React.JS also does not have computed properties out of the box (also, you can compute it pretty quickly). Event Handling also differs in React.JS and Vue.JS, also they both use virtual DOM, instead of traditional one.

Question #3. What are the major disadvantages and limitations of React.JS?

Answer #1
JSX, Poor Documentation, View Part

Answer #1
Bravo for not being afraid to list JSX as one of the main disadvantages of React.JS, as it can be described as both a blessing and a curse. JSX can be considered a barrier, especially for new developers, as it greatly complicates the learning curve.
As for the View Part, you should never forget and never shy away from mentioning the fact that React.JS only covers the UI Layers of the whole app in your interview, so the project would still need other technologies for the full toolset.
And the third major React.JS’ limitation is its poor documentation, which stand from constant development, which renders full proper documentation impossible.

Answer #2
Steep learning curve, Limited SEO options, Speed of development

Answer #2
Once again, the devil is in the details. While the steepness of React.JS’ learning curve is quite significant and the speed of development is bringing its fair share of problems too, React.JS is extremely SEO-friendly.

Question #4. What are the differences between React.JS and other Java scripts?

Answer #1
React.JS:
uses MVC framework, has eazy Real-time data steaming, has the largest ecosystem of open-source libraries

Answer #1
Unfortunately, you are wrong on this one. All of these features differentiate not React.JS, but Node.JS. It’s also worth mentioning here that Node.JS is used for creating backend, while React.JS covers only the UI side of the question.

Answer #2
React.JS:
uses TypeScript, uses MVC framework, has Built-in support for AJAX/HTTP/ Observables

Answer #2
We urge you to pay closer attention. React.JS does not use TypeScript, it uses JavaScript, hence the JS in the name.

Question #5. What are the major two types of components that can be declared in React, and when should you use one over the other?

Answer #1
Smart Components and Dumb Components.

You choose Smart Components when you need a component that is able to manage its own state and Dumb component when there is no need for state managing and/or the component is stateless.

Answer #1
The descriptions of and reasoning behind choosing these components are correct, but we do not use Smart and Dumb components in React.JS. Instead, the two major types of components in React.JS are Functional and Class components.

Answer #2
Functional Component and Class Component.

You should choose Class Components when you need the data to be transferable from one component to the other and Functional Component for JavaScript functions.

Answer #2
You are right! Components in React basically return a piece of JSX code that tells you what should be rendered on the screen. Thus, these two component types are the ones we use.

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