Top 50+ React Native Interview Questions and Answers 2020

Last updated on by Digamber

With the rise in popularity of mobile apps, the Mobile application development industry is thriving. A career as a mobile app developer is something every programmer seeks to fulfill. 

There are plenty of jobs available today for mobile app developers and web application developers. Getting a job is easy if you have the required skill set, but fighting the interview is not always easy. 

You could be asked well a chunk of questions on React native while appearing for a web application developer, mobile application developer, or React native application developer job interviews. 

That means you need to have a sound understanding of React Native and its functionalities. To save your time, we have compiled a lot of React native questions along with their answers in this article. 

 

Best 50+ React Native Interview Questions with Answers in 2020

Have a look at these mostly asked best 50+ React Native Interview Questions and their answers in 2020. Get ready to face any question on React Native thrown at you in the interview. 

Let’s get started. 

 

1. Tell us something about React Native?
React Native is a Javascript framework based on javascript React library. It is an open-source framework to facilitate native mobile application development. Facebook released React native framework to help developers build platform-independent mobile applications that utilize the only javascript. It focuses on native components rather than web components. 

2. What is the efficacy of the React Native framework?
React Native is a popular mobile app development framework with a large number of developers using and contributing to it. It has got certain advantages and powers, listed below are a few of them-

  • One can design a mobile application using javascript
  • It is a cross-platform framework. The code written on any device could run on ios or android platforms. Developers now don’t need to learn specialized languages to build ios or android applications like kotlin and objective C, respectively. 
  •  The cost to hire different developers for building applications for ios and android separately can be eliminated. 
  • If the learner already knows React.js, than it would be a breeze to learn react native. 
  • Unlike other frameworks, the apps developers created to React native are native ios and android apps. That means they use native components rather than web components. This makes them better performing in real-time. These apps are not like web applications in a mobile app.
  • It is faster to create applications as it comes with features like hot reloading functionality and live reload. 
  • It is an open-source 
  • A large community of React native developers keeps care of its bugs, performance, security, and other issues. 

3. Why would you choose the React Native framework over another application framework? 
Although, there are a variety of other application development frameworks available like ionic and Cordova, React native is distinct and has got certain advantages which are listed below-

  • React native is the framework to create real mobile applications, not web applications running on a mobile app platform. 
  • It is better in performance as React native applications are translated in machine code and run on mobile. 
  • It is not a hybrid app development framework, and it is more of a native application development framework. 
  • The application has a small bundle size. 

4. Is React native framework robust and trustworthy? Are there any big companies utilizing this framework?
React native is a robust way to develop robust applications for both ios and android. It has a large developer base, and even big companies use it to build their apps. Some examples are as follows:

  • Instagram is an application built on react Native, and as we know, it is capable of handling extensive interactions and processing. 
  • Other companies and organizations also rely upon react native for their application like Pinterest, Uber, Tesla, and Airbnb. 

5. How many React native components do you know about?
There are various components in React native, down are all of them-

  • View: the Component to build UI.
  • Image: the Component to display images. 
  • Text: to display text.
  • Text input: to get a text from the user through the keyboard. 
  • Scrollview: Component to host multiple views. 

6. Differentiate between development in Reactjs and React Native?
The reactive Native was introduced by Facebook years after the release of Reactjs. Both are open source technologies and related, yet they have their disparities like-

  • Reactjs is focussed on web application development, and React Native is great for mobile application development. 
  • React Native focusses on native components rather than web components, unlike Reactjs. 
  • We use tags like div, span, and other HTML tags to design the UI of the web application. On the other hand, we use to View, text import, and other components from the React Native library. 
  • It is not possible to access browser properties like window objects and local storage to React Native.
  • Both React Native and Reactjs are open-sourced, but different projects on Github. 
  • React Native and Reactjs have Different features and tool base to get started. 

7. How to write React components?
There are two techniques to write React components. These are listed below-

  • Functional Component
  • Class-based Component

8. Tell the number and name of threads that run in React native. 
The number of threads in React native is two, and they are as follows:

  • JavaScript thread
  • Main UI thread

9. What does the XHR module in React native do?
To post data on the Server, XMLHttpRequest is implemented by XHR. 

10. Explain Props in React Native?
They are properties of React native components. Props are parameters passed in the presentational Component to provide data. These parameters cant be changed. 

11. Differentiate React Native and React script?
React Native and React script are different in terms of:

  • React script uses a variety of languages like Vuejs, Angular, TypeScript, and JavaScript, but React native only consumes javascript. 
  • It is faster to develop applications to React Native and React javascript. React Native offers reusable codes and components to build apps faster. 
  • React native is more robust than React javascript. 

12. Is it possible to use Native code alongside React Native? 
Yes, it is possible to use Native code alongside React native. 

13. Is it possible to React native to combine native codes of android and ios?
Yes, it is possible, and in React Native, we can easily combine components of android or IOs written in java or swift. 

14. What Redux do in REACT native?
It is a standalone state management library. It simplifies data flow in an app. 

15. What is the difference between the React element and the React component?
The react element is used to display the look of the React component. 

React Component on the other side is a function capable of accepting input and returning a React element.  

16. Do you know the reason why React native has such bright animations?
The reason is the animated API of React native is serializable. That means the user doesn’t need to go through the bridge in every frame to send animations to natives. As the animation starts, js thread is blocked, the code is converted into native, the animations run smoothly and clearly. 

17. Do you know the use of StyleSheet.create()? 
The StyleSheet.create() is used in React Native to avoid passing a new style object by transporting the style only once through the bridge. It ensures opaque and unchangeable values. 

18. Explain the working of virtual DOM to React Native?
Virtual DOM, as the name suggests, is the in-memory tree representation of the actual DOM. It has lightweight elements. It gives DOM representation in a declarative fashion and allows us to change the UI when the state changes in an app. 

19. Explain the working of Virtual DOM? 
It records content, elements, and attributes. The whole UI is rendered when the data in virtual DOM changes. React distinguishes it with previous DOM and updates the DOM. 

20. Tell us about HOC?
HOC is the abbreviation for the Higher-order component. High order components or HOC is the functional programming procedure to use component logic. What this does is: it takes a component as an argument, and a new component is returned. It disintegrates the logic into smaller functions that are reusable. 

21. Are React Native and React any similar?
Yes, React Native and React share few familiar things like:

  • componentDidMount and other life cycle methods are similar.
  • The state and prop variable are identical.
  • Management libraries are exact—Redux, for example. 
  • The component architecture is exact. 

22. How React relates to React Native?
React, a javascript library is the basis of React Native. As we know, React Native is used to building mobile applications using javascript, but React Native consumes React for defining business logic and Application UI construction. React Native uses virtual DOM, React updates a real DOM, and enables the working React Native. 

23. How to test if a node_modules would run on React Native? Do you know which will run fine?
All node_modules, as any real javascript library, would run fine if they don’t rely upon Node.js run-time modules or web-specific intentions. There is no defined way to test the compatibility of any node_modules. 

24. Do you know about the interaction manager?
It is a native module in React Native. The interaction manager can postpone the implementation of a function until an “interaction” finishes. 

25. Why do we use the Interaction manager in React Native?
The interaction manager is helpful in React Native to make the execution of function takes place once the animation happens. 

26. What do you mean by the State in React Native?
Like props, State could be utilized to alter a react component, but the state values of the react component may change during the lifecycle of the Component. setState method is useful for developing the State of a component, changing it directly is not advised. 

27. What are the steps to create and start a React Native app? 
Down are the ways to create and start a React Native app:

  • The first step is to install node.js.
  • Then one should install environment for react native, the command given is useful for the same: $ npm install -g create-react-native-app  
  • Now you can create a project by utilizing the following command: $ create-react-native-app MyProject. 
  • Use this code: $ cd MyProject to move to your project. 
  • Use this to start the project: $ npm start. 

28. Can we use any component in React Native?
Component utilized in React uses DOM elements that are not supported in React Native. Thus, no, only components made for React native can be used in React Native. Though, you could find a component that could be used in both React and React Native. 

29. List the difference between React Native and Xamarin?
Xamarin is an open-source framework launched in May 2011 by Xamarin Company. Using Xamarin, we you can build iOS, Android Windows, and Mac apps. That means it is a cross-platform framework, but it uses c# for development rather than javascript, unlike React native. 

30. Why is the use of style in React Native?
The style in React Native makes applications look attractive. It is a crucial component. Javascript objects can style applications to React Native. 

31. Tell us about Refs in React Native?
If one wishes to access DOM elements or Component’s instance directly in React, we can make use of Refs in React Native. If you don’t to use props or reorder the entire Component, React refs can do the work for you. 

32. In React Native, what is the use of Keys?
Keys could be helpful in determining what items have been changed, deleted, or updated as they are the unique identifiers. Keys are used inside the array. 

33. What is the syntax of HOC in React native?
The syntax of Higher-order components is as follows:

const NewComponent = higherOrderComponent(WrappedComponent);   

34. In what condition do we prefer using a class component over function component?
In case, the Component has a life cycle and State, we use class component over a functional component. 

35. How React Native deals with a variety of screen sizes?
React Native deals efficiently with different screen sizes using the following:

  • Flexbox provides uniform layout on screen with different sizes using its three properties: justify-content, flex-direction, alignItems. 
  • Dimensions can style the page accurately on screen with different sizes. 
  • Pixel ratio class can be utilized to access the pixel density of the device and render the image accordingly. 
  • The aspect ratio sets the height. 
  • Scrollview, a scrolling container that contains multiple components and can be scrolled both vertically and horizontally. 

36. Explain the storage system consumed in React Native?
The storage system in React Native stores the data globally in the form of key-value pairs and is an unencrypted, asynchronous, persistent, and simple system of storage. The AsyncStorage class is used in react-native to store data.

37. How React Native loads data on Server?
React Native consumes Fetch API to load data on the Server when needed.  

38. Tell us about Animations in React Native?
Animations are the transmission of one image to another or manipulations of I ages to look like moving objects. Animations in React native are useful for a variety of purposes, like adding extra efforts to improve UI and UX. A variety of ALI’s is available in React native to use animations. Some of them are Animated API and Layoutanimated API. 

39. Tell us about the accessible UI components in React Native?
The favorable UI components are:

  • Material UI
  •  Semantic UI
  • Ant Design
  • React Bootstrap
  • React Toolbox

40. Have you heard of Listview?
It comprises of a list of items that are displayed in a scrollable vertical list. It is a core React native Component. 

41. What is the way to integrate new features in your existing native applications?
The exact steps to integrate new features in existing native application differs from platform to platform. The general steps to incorporate new features in your existing native application are as follows:

  • You would first need to set up a directory structure.
  • The second step is to install JavaScript dependencies.
  • Then you would need to Configure permissions.
  • The next thing to do is Code integration.
  • At last, you can test your integration.

42. Do you know about the Gesture responder system?
The gesture responder system is useful in handling gestures and their life cycle in the application. The Component could work with gestures with a gesture responder system. 

43. How Native apps well on multiple platforms?
React Native is a cross-platform development framework. Apps with react components would work fine on any platform, be it ios or android. Moreover, React native have features by which you could separate organize and separate codes on different platforms:

Platform module in React native is capable of determining the platform on which the app is running and make use of platform-specific file extensions, which could load required platform files.

44. Do you know about NPM in React native?
NPM is responsible for installing a command-line interface or CLI in React native. 

45. What is the use of a React native packager?
React native package is useful in a variety of operations like-

  • Merging all the code into one javascript file. 
  • It is capable of translating the js code that your device has trouble understanding. 
  • The conversion of an image in an object is done by React native packager.

46. What do you mean by component-driven development?
The process of breaking the entire UI into various minor reusable components and developing them alone. Thus building entire UI by adding those independently built reusable components. It leads to faster a d robust development of applications. It results in less code, thus less maintenance and fewer bugs to fix. 

47. What do you mean by the dumb Component in React Native?
Dumb components are also known as presentation components. Components can be categorized into dumb components and container components, depending on their roles. 

Presentation components with stying and presentation, as the name suggests. They may have some container component or another dumb component inside them. They usually just renders the data by creating markup for it. These type of components don’t have their states generally. 

48. What is the difference between controlled and uncontrolled components?
If the value displayed on UI by the Component is determined by form input, then it is called a controlled component. On the other side, if the State determines the value, then it is called an uncontrolled component. 

49. Do you know some timer related functions in React Native? If yes, list them. 
There are various timer related functions available in React native. Sone of them are listed below:

  • setTimeout, clearTimeout
  • setInterval, clearInterval
  • setImmediate, clear immediate
  • requestAnimationFrame, cancelAnimationFrame

50. How many Native elements in Reactive Native do you know?
The following are some Native Elements in React Native:

  • Keyboard Events
  • Focus Events
  • Clipboard Events
  • Composition Events
  • Wheel Events
  • Media Events
  • Image Events
  • Animation Events
  • Form Events
  • Mouse Events
  • Pointer Events
  • Selection Events
  • Touch Events
  • UI Events
  • Transition Events
  • Other Events
Do you know about FlatList in React Native and its advantage over scrollview?
FlatList is a component used to display a line of data. FlatList is often used to display long lost of data where the number of items could fluctuate. It renders only the element in focus on the screen, not the whole list, thus it is better to use FlatList rather than scrollview.

Conclusion
These were some of the React native interview questions. These questions are often asked in interviews and are popular questions to test one’s knowledge about React native. 

Released in 2015, React Native is considered to be an upgrade to React. Despite Reactjs and React Native both being introduced by Facebook, they have their use and differences. 

No matter what framework you use to develop robust mobile applications, you should always have a clear understanding of other technologies in trend. This would make you a better professional. 

As I said in the beginning, the mobile development industry is flourishing, and it’s worth getting into a mobile development career. 

These questions are created with an aim to help you ace your next developer interview. I hope these questions were helpful. Thanks for reading this article on 50+ top React Native Interview questions. 

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Digamber

Digamber Rawat is from Uttarakhand, located in northwestern part of India. He is a Full-stack developer by profession and a primary author of this blog.