Top 50+ React Native Interview Questions with Answers In 2019

Essential React Native Interview Questions in 2019

 

React Native Interview Questions
React Native Interview Questions

 

React Native is dominating the world of Cross-platform Mobile App development. If you are preparing or learning about react native, then this post worth reading for you. Here, through the series of React Native Interview Questions, we are trying to cover all basic concepts.

Our React Native developer’s team has prepared a great list of beginner’s level React Native Interview Questions.

These essential react native interview questions would help you “How to crack react native interview?

This guide will help both React Native Job aspirants and interviewers to refer the set of basic fundamental React Native Framework. 

Q1 – What is React Native?

React Native is Facebook’s JavaScript based framework for developing cross-platform mobile applications. React Native allows developers to create real, native mobile apps both in Android and iOS platforms. It’s based on React which is facebook’s JavaScript library for designing User Interfaces. Most of the application code can be shared among Android and iOS platforms.

React Native framework offers faster mobile development, and more efficient code sharing across Android, and iOS platforms without compromising the end user’s experience or application quality.

Q2 – What is the main difference between react and react native?

ReactJS is just JavaScript library whereas React Native is complete mobile development framework. React or ReactJS was developed to just focus on better UI performance. React Native comes with native modules and components that improve performance as well as render the UI components with native API’s. This is the common React Native Interview Questions.

React Native allows developers to write common code and share the business layer across platforms (Android & iOS). 

Using React Native framework, developers need not to rebuild the same application on Android and iOS separately.

Q3 – What are the main advantages of building Mobile App in React Native?

  1. React Native is web based which gives the developer an advantage if the developer has previous experience with HTML, CSS and especially JavaScript.
  2. Code Re-use & Knowledge Sharing across platforms (Android & iOS)
    Using the React Native organizations need not to have separate team for Android and iOS development. React Native allows developers to share same knowledge and code across platform development.
  3. React Native translates the UI components to actual native UI components using native API’s (Android or iOS)
  4. Better UI performance – React native works separately from the main UI thread.
  5. Developer Experience – Web Developers with knowledge of HTML, CSS, Bootstrap, JavaScript can write high performance Apps. If you are developer and have ever developed Mobile App in Android or iOS platform, using React Native you will be surprised how easy  it’s to do the same. React Native provides developers with intelligent debugging tools and error reporting mechanism. React Native Interview Questions.

Q4 – Is there any disadvantage of React Native?

Honestly speaking, as such I don’t see any disadvantages of using React Native for Mobile Apps DevelopmentBut, the only downside of React Native is that it’s growing and improving. Some native features of Android and iOS are yet to be supported in upcoming releases of React Native.

React Native Interview Questions..

 

Q5 – Mention some Famous Mobile Apps built in React Native?

There are following largest organizations using React Native for mobile apps developed in RN [React Native Interview Questions]:

1. Facebook
2. Instagram
3. Facebook Ads
4. Walmart
5. Bloomberg
6. SoundCloud
7. Uber Eats
8. Tesla
9. Skype
10. Pinterest
11. SalesForce

12. 2048 Game
13. KFC application
14. Myntra

Q6 – What are main components of React Native?

Before starting development with any new technology, it becomes necessary to understand the high level components of the React Native framework. A component is very basic UI element in React Native. The React Native app is a group of various UI components. React Native ships with inbuilt components.

React Native Interview Questions

React native have the following core components:

Basic UI components in React Native

1. View

View in React Native is equivalent to <div> tag in HTML. It is a content area where the actual UI components (Text, Image, TextInput, etc) would be displayed. View is used to organize the content in good manner.

2. Text

Text is a very basic built-in Component which displays text in the Application.

3. Image

A component for displaying images.

 

4. TextInput

This component is used to take user input into the App.

 

5. ScrollView

Its is a scrolling container that can host multiple components and views that can be scrolled.

6. StyleSheet

Similar to CSS stylesheets, Provides an abstraction layer similar to CSS stylesheets.

Important Trick to remember React Native Components

<div> = <View>
<span> = <Text>
<li>, <ul> = <ListView>
<img> = <Image>

User Interface Components in React Native:
1. Button – A basic button component for handling touches that should render nicely on any platform.
2. Switch – Renders a boolean input.
3. Slider – A component used to select a single value from a range of values.
4. Picker – Renders the native picker component on iOS and Android.

 

React Native Interview Questions

ListView components in React Native:
1. FlatList            – A component for rendering performant scrollable lists.
2. SectionList    – Like FlatList, but for sectioned lists.

Android Specific components in React Native [React Native Interview Questions]
React Native provides some wrapper components for common Android classes like Toast, ProgressBar, ViewPager, etc:

1. DatePickerAndroid – Opens the standard Android date picker dialog.

2. DrawerLayoutAndroid – Renders a DrawerLayout on Android.
3. BackHandler – Detect hardware button presses for back navigation.
4. ProgressBarAndroid – Renders a ProgressBar on Android.
5. ToastAndroid – Create an Android Toast alert.
6. ViewPagerAndroid – Container that allows to flip left and right between child views.

Next, commonly asked React Native Interview Questions.

React Native Interview Questions

Q7 – How does React Native Works?

While learning any new framework like React Native, it become very important to first understand how React Native works at low level under the hood. React Native lets you build mobile apps using only JavaScript. React Native Interview Questions

Every React Native application has 2 main threads:

1. Main Thread in React Native

Each React Native application main thread running, this is also known as UI thread. This thread is responsible for rendering the native Android/iOS UI to the app screen. It handles UI rendering and handle user experiences.

2. JavaScript Thread or JS Thread in React Native

The JS thread or JavaScript thread is responsible for executing the javascript code inside the application. Its runs all the business logic code in separate JS virtual engine. It handles API calls, events and much more..

Interestingly, these 2 threads never communicate with each other in any way.

Refer step-by-step guide to understand Laravel Web development Framework:

 

Q8 – What is a Prop in React Native?

This is most commonly asked React Native Interview Questions.

  • Props stand for Properties in React Native.
  • Prop is type of data that never change.
  • Props are used to control data that cannot be changed.
  • Props as compared to States are Immutable.
  • Props are fixed throughout the lifetime of a component.
  • Props are used to customize various Components which are created and give it different parameters.

The main usage of props is that they can be passed by a parent component to its child components.

Prop Example in React Native [React Native Interview Questions]

import React, {Component} from ‘react’

class Topic extends Component {
render{
return(
<div>
{this.props.name}
</div>
)
}
}

Q9 – What is a State in React Native?

  • State is another type of data that can be changeable (mutable)
  • State is bound to single React Native component and can be changed throughout the lifecycle
  • States allows developers to dynamically change the content at any point of time in response to certain events.
  • States are initialized in the constructor and setState() function used to change content of state.
  • React Native Interview Questions

Q10 – What is Style Vs Stylesheet in React Native?

Style is a set of attributes used to design of the UI part of the application. It consists of colours, strings, layouts, etc. Style in React Native is similar to CSS in HTML.

Stylesheet is a group of styles. Stylesheet are used when grows in size then its cleaner approach put all styles in single place.

Styles Example  in React Native

import React, { Component } from ‘react’;
import { AppRegistry, StyleSheet, Text, View } from ‘react-native’;

const styles = StyleSheet.create({
bigBlue: {
color: ‘blue’,
fontWeight: ‘bold’,
fontSize: 30,
},
red: {
color: ‘red’,
},
});

export default class StylesExample extends Component {
render() {
return (
<View>
<Text style={styles.red}>just red</Text>
<Text style={styles.bigBlue}>just bigBlue</Text>
<Text style={[styles.bigBlue, styles.red]}>bigBlue, then red</Text>
<Text style={[styles.red, styles.bigBlue]}>red, then bigBlue</Text>
</View>
);
}
}

Inline Styles in React Native:

Like HTML inline styling, React Native also support inline style to be used inside the components (tags). 

 

Example Inline styles in React Native

<Text>
This is  <Text style={{fontStyle: “italic”}}>inline</Text> style
example <Text style={{fontWeight: “bold”}}>in React Native</Text>.
</Text>

To be Continued.. We will keep posting new series of React Native Interview Questions

Subscribe to our Blog @ TechCluesBlog

Further Reading [React Native Interview Questions]

  1. React Native Official Guide
  2. Tutorials Point React Native Guide

Leave a Reply

Your email address will not be published. Required fields are marked *