React Native Interview Questions

Being single-handedly one of the most used and preferred mobile application frameworks, React Native is based on JavaScript and, surprisingly, developed by Facebook.

One of the most significant and discernible features of React Native is that it has been adopted by more than 8000 major tech giants, including Facebook and Airbnb. Given its potential, popularity, and opportunities, React Native is one of the best fields to start a career and work with your dream companies.

Being a React Developer is seriously beneficial, especially in today's technological environment, where global clients are potentially outsourcing React developers because of how efficient and reliable this framework is.

Expertise in the react development environment is no less than a Trump card, as it allows you to develop applications on platforms like Android and iOS. Companies that require personalized applications for their platforms have no better option than approaching React Developers.

Overall, the field of React Native is very promising and ensures growth with a scalable career. However, seeking a career as a React Developer requires adequate preparation and knowledge. That's why we have prepared a list of React Native interview questions to help you outperform your following interview and answer all questions asked quickly.

In this article, we will cover the following:

• Basic React Native Interview Questions for Freshers
• React Native Interview Questions for Experienced
• React Native Coding Questions

Most Frequently Asked React Native Interview Questions

What are the key benefits of using React Native for mobile applications? What are React Native apps? Why do we install Watchman software to set up a React Development Environment on MacOS? What do you mean by higher-order components (HOC) in react native, and how are they used? What's the difference between functional and class components? How can we create a basic button in React Native? What’s the difference between Shadow DOM and Virtual DOM? What is Async Storage in React Native? What are some companies or applications built using React Native? What’s the significance of keys in a component in React Native?

Basic React Native Interview Questions for Freshers

Q1) What do you mean by React Native?

Ans: React Native is an open-source tool introduced by Facebook. We use this tool to develop Android and ios applications. In a way, react native is similar to React JS. React JS is a library developed by Facebook and XML.

React Native is a cross-platform tool that can run on any platform. It reduces software development time significantly. This is because it supports building applications using JavaScript and ios together.

Q2) What is JSX?

Ans: JavaScript XML (or JSX) is faster. It is an HTML/XML template syntax that React widely uses. It helps create templates efficiently. JSX also allows the integration of HTML into JavaScript. It extends the ECMAScript, which enables the XML/HTML-like text to coincide with the React code.

Q3) What are the key benefits of using React Native for mobile applications?

Ans: React Native is an ideal platform for building mobile applications effectively. Also, it deploys pre-developed components and allows the reusing of codes for building other applications. Besides, this tool enables customization and saves time considerably. The react native community is large and active.

Q4) State the differences between React Native different and React JS?

Ans:

React Native	React JS
React Native is a framework that we use to develop mobile applications	React JS is another framework that we use to build web applications
it doesn’t use HTML tags	It uses HTML tags
It lacks in security aspects when compared with React JS	It is a highly secure framework
It comes with a built-in navigator library	It uses React-router for navigation.

Q5) What is DOM in React Native?

Ans: Document Object Model (or DOM) is a structured representation of all kinds of HTML elements present in a webpage or web app. Simply put, DOM is the entire UI of the application we develop in React Native.

Q6) Outline the various vital components of React Native?

Ans: The following are the vital components of React Native:

• View - It is the fundamental built-in component used to build a mobile application's UI. This component helps to build applications in both ios and Android. You can view the content in view.
• Style - It refers to the different components in the applications that make the applications attractive. React Native uses JavaScript objects to style applications.
• Text - It displays all the textual content of applications. It collects the text inputs from users with the help of a primary component text input and shows them in the applications.
• States – They control all the components in your React Native framework. All the variable data can be stored in the states.
• Props – It passes data to different components of the framework. It connects the container and the presentation component. It cannot change the data.

Q7) What are React Native apps?

Ans: The great thing about React Native is that they quickly load applications on mobiles than browsers. The applications are not hybrid and can't run on WebView components.

React Native apps are usually built and designed in JavaScript. It uses different native components to run on mobile devices.

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Q8) List the steps required to create and start a React Native application.

Ans: We should use the steps to create and start React Native applications.

Step 1 – First, install the Node.js software on devices

Step 2 – then, install the react-native environments using the below command

$ npm install -g create-react-native-app

Step 3 – Next, create a project using the below command

$ create-react-native-app MyProject

Step 4 - Navigate to your project using the following command 

$ cd MyProject

Step 5 – Lastly, run the below command to start the project

$ npm start


Q9) What do you understand by Redux in React Native, List the essential components of Redux?

Ans: Redux is a predictable state container used by JavaScript applications. It allows a single container to manage the data flow of applications. It helps write applications that can run on any platform.

Here are the components of redux.

• Actions – They send data from an application to a store. They dispatch the information and perform the changes required to the application.
• Reducers – They are the components that perform things that actions cannot do. It specifies the changes in applications. Once an action is sent for a state change, then reduces, make the necessary changes to the state.
• Store – Reducers play a vital role in the creation of stores. This is because they hold the complete state of an application. It is always better to use a single store instead of multiple stores.
• Components – They store the UI of applications and save all the changes required.

Q10) What is the role of the state in React Native, and how can we use it?

Ans: State in React Native controls the components in the React Native framework. Also, we can store variable data in the state.

Below is the code that helps create a text class component using state data:

import React, {Component} from "react";
import {Text, StyleSheet} from "react-native";
class TextExample extends Component{
  constructor (props){
   super (props);
    this. state = {
        titleText: "What is React Native?",
        bodyText: "React Native is a JavaScript framework."

         };

     }

}

React Native Interview Questions for Experienced

Q11) Why do we install Watchman software to set up a React Development Environment on MacOS?

Ans: Watchman is an open-source project developed by Facebook. This software watches the files in the framework and monitors any changes. Moreover, it can also be coded to trigger actions based on different activities in the framework.

Watchman is preferred for React Development because it allows the hot reloading feature of React Native. It helps developers to build applications faster than normal.

If the developer makes any changes to the project file, the Watchman software will reflect the changes automatically. The hot reloading feature speeds up the development process for different applications.

Q12) How can we style a component in React Native?

Ans: Style refers to the different elements in the web or mobile applications that make them attractive. The core components of React Native accept a prop. The same prop could be a simple JavaScript object.

With this feature, various styles can be passed on to the application. 

However, a complex component calls for using StyleSheet to create multiple styles in a single place.

Here’s an example of a StyleSheet.

const styles = styleSheet create(f
       container:   {
               borderRadius: 4,
               borderWidth: 0.5,
               borderColor:'#d6d8da',
       },
       title:  {
               fontSize: 19,
               fontWeight:'bold',
       },
       activeTitle: {
               color:'red',
       },
});
<View style={styles.container}>
       <Text style=([styles.title, this.props.isActive && styles.activeTitle]} />
</View>

Q13) What are Props in React components?

Ans: Props are parameters that allow a developer to customize a component during the creating and re-rendering process.

Props are the instructions passed on to a React component.

A component can show a different UI if developers pass different props values. Props allow using the same components at other places and remain fixed for the entire component lifecycle.

Read these latest ReactJS Interview Questions that help you grab high-paying jobs!

Q14) Explain Props Drilling and how to avoid it.

Ans: Threading or Props Drilling is a concept that allows developers to pass the data from a parent component to the exact child component.

However, different components that own the props pass it down the chain.

Here’s how to avoid Props Drilling:

1. React Context API
2. HOC
3. Redux or MobX
4. Composition
5. Render Props

Q15) How is the React Native code processed to show the final output on a mobile screen?

Ans: There are a few steps for the same:

• First, the main thread starts the execution, loading up the JS bundles.
• As the JavaScript code loads, the main thread sends it to another JS thread.
• As React starts rendering, the reconciler generates a new virtual DOM. It sends the same changes to another thread.
• At this stage, the shadow thread calculates the layout and sends the objects to the main thread.

As the main thread renders something on the screen, the shadow thread sends the generated layout to the main thread.

Q16) What do you mean by higher-order components (HOC) in react native, and how are they used?

Ans: The Higher-order components in React Native refer to the pure functions. They take different components and return the new components to the development environment. 

HOCs are advanced techniques that rise from React’s compositional nature.

HOCs have a common purpose: to reuse the stateful logic throughout all the components.

Q17) How can a CSS flexbox lay out a React Native UI?

Ans: The View component in React Native is the component that displays the set to flex. Flex is used to expand a component based on the available space in the UI to make it visible and responsive.

The width of the child element can be changed by giving the flex property a higher value. When the value of the flex rises, the ratio of space of a component also rises.

A component can expand to fill the available space if the parent has more than zero dimensions. The parent element must have some width set to make the flex work. If not, the element will consider the width as zero and won’t be visible on the UI.

Q18) What's the difference between functional and class components?

Ans: Stateless components are also known as functional components. They accept props and return HTML. 

Functional components give the solutions without using state. We can define them with or without arrow functions.

Here’s a common example:

import React from "react";
 const Friend = (props) =>
        <div>
        <h1> Hi, {props.name}</h1>
        </div>
);
export default Friend;

On the other hand, class components are also known as stateful components. They are the ES6 classes that extend the component class from the React library.

Class components implement the logic and state and must have the render() method when returning HTML.

Here’s a common example:

Q19) What are the ways a developer can optimize an application?

Ans: Developers can optimize an application in different ways. Some of them are listed below.

• Compressing the raw JSON data instead of storing it in its original format
• Compressing the images and other graphics
• Optimizing the native libraries and the number of state operations
• Creating low-sized APK files for CPU architectures

Q20) Describe the life cycle of a React component.

Ans: The lifecycle methods posed by the react components can be shown below:

function averysimpleHOC(WrappedComponent) {
  return class extends React.Component{
    render() {
      return <WrappedComponent {...this.props}/>;
    }
   }

}

The same lifecycle methods can be divided into three categories:

Mounting - Mounting is the first phase of the component. The constructor receives the props as an argument from the parent component. This returns the state object to avoid the render, which further renders the JSX. Finally, the componentDidMount is invoked.

Updating - Components start getting an update through a change in state or props. In both cases, we use the getDrivedStateFromProps method. Further, we use the shouldComponentUpdate methods to get initiated. Also, if one method returns true, the other component gets updated. Otherwise, the component update is aborted.

Unmounting - The componentWillUnmount lifecycle method is initiated before the unmounting of a component.

Q21) How can we create a basic button in React Native?

Ans: React Native has a Button component that allows developers to include a button in the application. 

A platform-specific button changes the look of a button. And it depends on whether the application runs on iOS or Android. 

The button component displays two props: 

• Title – it is used to display the text on the button
• onPress – it is a form of a ‘call to action’ when the user clicks the button. 

Q22) What’s the difference between Shadow DOM and Virtual DOM?

Ans:

Virtual DOM	Shadow DOM
It avoids unnecessary changes to the DOM, which are practically expensive.	It allows a single custom element implementation which is combined with complex DOMs.
It allows the collection of a variety of changes applied once. So every single change causes re-rendering and affects the performance.	An entire web application with complexities can be added to a page by an import.
Re-rendering happens once changes are applied to the DOM	Simpler, and reusable components can be implemented as custom elements.

 Q23) How do you debug the React apps, and what tools can you use?

Ans: There are a few ways to debug your React Native application. As React Native is suitable for both iOS and Android environments, a few different problems can be encountered, and a variety of tools to fix these problems.

Developer menu - The developer menu consists of some of the most efficient ways to debug and access the debugging tools. This menu consists of

• Reload
• Debugging JS Remotely
• Live Reloads
• Hot Reloading
• Toggle inspector
• Show Perf Monitor

Chrome Dev Tools - The Chrome DevTools can debug React Native apps. However, proper same-routed WiFi is essential. In the developer menu of your OS, we can select “Debug JS Remotely” and it will open the default debugger.

React Developer Tools - The React Developer tools can only be assessed from the desktop application. These tools allow debugging React components and styles according to preference.

React Native Debugger - Using Redux in our React app is a good debugger. It's a desktop app integrated with the developer tools of Redux and React in one app.

Checkout our Blog on  Events in JavaScript with Examples

Q24) What is Async Storage in React Native?

Ans: Async Storage is the React Native that’s equivalent to local storage from the web. 

It's a community-manipulated module for React Native that's not shared between apps, as every app has its sandbox environment without any access to data from other apps.

 

React Native Coding Questions

Q25) What’s the ScrollView component of React Native?

Ans: The ScrollView component is a scrolling controller in React Native that can host different components and Views. 

This function allows users to scroll horizontally and vertically on the applications.

ScrollView works to present a small number of things of a limited size. All kinds of elements of a ScrollView are rendered even if they aren’t present on the screen of the user.

DO USE ASYNC STORAGE WHEN...	DON'T USE ASYNC STORAGE FOR...
Persisting non-sensitive data across app runs	Token storage
Persisting Redux state	Secrets
Persisting GraphQl state
Storing global app-wide variables

Q26) How is FlatList better than ScrollView?

Ans: The React Native framework provides the FlatList component to display a long line of data.

FlatList is an ideal component for viewing long data lists where the items might change over time.

Unlike ScrollView, the FlatList only renders those elements visible on the screen rather than all the elements simultaneously. It also provides a performance boost over the ScrollView because FlatList creates a card at runtime where the user starts scrolling the page.

Q27) How is a controlled component different from an uncontrolled one?

Ans: React Native components could be divided into two categories

Controls like text input with a value attribute could be used to display the user input value on UI.

However, if the state of the component maintains the state of the component, then these components refer to as controlled components.

Controlling a component is done by assigning the component's state as the value of control elements and adding the callback methods. These methods update the state of every value change event.

Q28) What are some companies or applications built using React Native?

Ans: Companies and huge platforms like Facebook, Airbnb, Instagram, Uber, and Tesla are developed by React Native. That's why the popularity of React Native framework has grown significantly.

Airbnb, one of the first major companies to adopt React Native, open-sourced many React Native libraries built on the React Native framework.

Their famous libraries included Lottie, which made it easier to create animations work in React Native.

Further, a lot of significant companies heavily depend on React Native. They can launch their applications on platforms like Android and iOS.

Checkout:[Functions in JavaScript]

Q29) What is the use of Network Security and SSL Pinning?

Ans: A Secure Sockets Layer (or SSL) is a protocol that establishes encrypted links between computers connected to the internet.

SSL binds the identities of computers to cryptographic key pairs through different documents known as X.509 certificates. Every part has a private and public key. The private key is kept secure, but at the same time, the public key is distributed as a certificate.

On the other hand, Pinning is such a feature that improves the security of a site relying on an SSL certificate.

Mobile applications typically use SSL to communicate with the server to protect data transfer from one device to another. With SSL implementation, apps trust the server with a certificate authorized by the OS trust store.

Q30) How is a React Native app made to feel smooth on animations?

Ans: React native apps works smoothly by avoiding expensive operations during interactions and animations. 

Since React Native has a single JS execution thread, we can use the InteractionManager to schedule the long-running work to complete the previous animations or interactions.

Applications schedule tasks to run after interactions by the following code:

InteractionManager.runAfterInteractions(() => {
// ...long-running synchronous task...
});

Q31) How can you define a dumb or presentational component in ReactJS?

Ans: As the application size grows on React JS, it will form various small/big components. This is an ideal stage to categorize and decide the roles for every element.

Based on these roles, the components are divided into two parts:

• The presentational component - stateless components.
• ·The container component - stateful components.

The presentational component has the following behaviour:

• it can contain presentational as well as container components inside
• They have some DOM markups and styles of their own
• It is concerned with presentation and styling
•  It doesn’t specify how the data is loaded
• It receives data and callbacks exclusively via props
• Unless they need performance optimization or lifecycle hooks, it is written as functional components.

Q32) How is ‘state’ managed in a bigger React native application?

Ans: React follows a component-driven development approach. It means that there must be some written several stateful or stateless reusable components. We can fuse them into building a single application.

As the application gets bigger, there are instances when one component wants to access a state of other components. There needs to be a dependent component as the children are components of the same parent component and communicate via callbacks. 

The exact solutions work for smaller applications as well.

However, passing the callback from parent to children elements is daunting for large applications. That’s where Redux effectively maintains the state of the large React Native applications.

Redux Native provides a store that allows developers to write actions and reducers to modify the state in the store. Any component can connect with the store using Redux’s high-order component connect.

Q33) What’s the significance of keys in a component in React Native?

Ans: In case there's ever an iteration through an array to create a list of components, and if a developer misses adding a key attribute, React displays a warning that the key isn't assigned to the elements.

The use of keys in React Native is to help identify the unique virtual elements with the associated data that drive the UI. It helps React optimize the rendering by recycling all the components' existing elements.

React also uses the user-given strong values to identify the nodes and decides whether the nodes need to be updated based on these keys. The same keys need a unique number or string by which React reorders the elements instead of re-rendering them.

Q34) Can React Native be used to build television applications?

Ans: The simple answer is yes.

TV device support has been implemented to make existing React Native applications work on Apple and Android TV with barely any changes required. Since iOS and TvOS APIs are quite similar, making React applications work on televisions makes a lot of sense.

However, much emphasis is laid on building TV apps, so whether to remove them from the core library is being discussed. So while React Native could be used to build TV apps, the community isn’t prepared for the same yet.

 

Conclusion:

Preparing for React interview questions might take time, so you'd have to prepare enough and be well-acquainted with every React Native fundamental. However, there’s still a lot to learn. You can bookmark our page for future references and keep brushing your knowledge about React Native framework.

If you want to groom your knowledge of React Native, you can attend courses in Tekslate and get a certification. After attending the interview, if you find any other questions in the blog, please post them in the comment section below. Our experts will include them in the blog along with the best possible solution to help other learners learn from your experience.