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40+ [REAL-TIME] React Native Interview Questions and Answers

Last updated on 13th Dec 2022, Blog, Interview Question

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1.What is Virtual DOM?

Ans:

Virtual dom is Associate in Nursing in-memory tree illustration of the $64000 DOM with light-weight parts. It provides a declarative method of DOM illustration for Associate in Nursing app and permits to update UI whenever the state changes.

2.What are some ways in which of styling a react native component?

Ans:

  • Inline styling.
  • StyleSheet.
  • Styled parts.

3.What is the distinction between RCT & RNT?

Ans:

RNT Let’s say you wish to use your own custom code written in iOS or robot. you have got to prefix your native files with RNT. The native React libraries provided by Facebook are prefixed with RCT.

4.List the core parts of React Native?

Ans:

View: it’s the essential integral part accustomed to building the UI of Mobile apps. The read is analogous to the div in HTML. it’s a content space wherever you’ll show your content.

States: it’s accustomed to managing the parts. The variable information is often held within the state. it’s mutable suggests that a state will amend the worth at any time. Props: Props are accustomed to pass information to the various parts. it’s changeless suggests that props cannot amend the worth. It provides an association between the instrumentation part and a presentation part.

Style: it’s a necessary part within the net or mobile, that makes the applying enticing. React Native doesn’t need any special language or syntax for styling. It will vogue the application of the JavaScript object.

Text: This part displays text within the app. It uses the essential part textInput to require text input from the user.

ScrollView: it’s a scrolling instrumentation accustomed to host multiple views. It is often accustomed to render the big list or content in sight with a scroll bar.

5.What is JSX?

Ans:

JSX could be a method for writing xml code beside javascript, called javascript extension. It’s used most of the time to make react native user interfaces.

6.What are native apps?

Ans:

  • Native mobile apps are the foremost common style of app.
  • They are designed for specific platforms and are written in languages that the platform accepts. For instance, Swift and Objective-C for native iOS apps and Java or Kotlin for native robot apps.
  • Native apps also are designed to exploit the particular Integrated Development surroundings (IDE) for the chosen operational systems.

7.What is Render () in React Native?

Ans:

It is obligatory for each react native part to own a render (). One single react part is returned by Render that’s illustration of native DOM part.

8.What is networking?

Ans:

It provides Fetch Functions to request HTTP Requests to a different server.

9.What are the benefits of native apps over hybrid apps?

Ans:

  • They work with efficiency as they’re designed for that specific platform.
  • Native apps are responsive on all the platform-specific devices.
  • They are in no time and therefore the best within the app performance.
  • Native apps integrate with mobile hardware.
  • They have interactive and intuitive programmes (UI) and User expertise (UX) as per the user expectations supported by specific platforms.

10.What are React Native Apps?

Ans:

React Native Apps aren’t net applications. These styles of apps are running on mobile devices, and can’t load over the browser. Also, they’re not hybrid apps that build over Ionic, Phonegap, etc.Which might run over the WebView part. They’re the $64000 native apps inbuilt one language JavaScript with the native parts to run on mobile devices.

11.Name a minimum of one vogue property that may increase tappable space around a component?

Ans:

  • Padding (and conjointly paddingVertical, …Horizontal, …Left, …Right, …Top, …Bottom).
  • minHeight and minWidth. hitSlop.
  • Make Tappable areas larger.

12.What are parts of Redux?

Ans:

  • Action.
  • Reducer.
  • View.
  • Store.

13.Name many corporations that are designed to exploit React Native?

Ans:

Facebook, Airbnb, Instagram, Pinterest, Tesla, Uber, etc.

14.What is the distinction between React part and React Element?

Ans:

React part is either a category or a performer that accepts input files, and returns React parts. On the opposite hand, react part doesn’t produce react part, however instead it solely displays its look.

15.How to take a look at if a node_modules would run on React Native? Does one understand which is able to run fine?

Ans:

All node_modules, as any real javascript library, would run fine if they don’t depend upon Node.js run-time modules or web-specific intentions. There’s no outlined thanks to take a look at the compatibility of any node_modules.

16.What are the best UI parts for React Native?

Ans:

  • Material UI.
  • React Bootstrap.
  • Semantic UI.
  • React tool cabinet.
  • Ant Design.

17.What is the distinction between React Js and React Native?

Ans:

    React JsReact Native
    Reactjs are often delineate as a base by-product of React DOM, for the online platform. React Native could be a base by-product in itself, which implies that the syntax and work flow stay constant, however parts alter.
    Reactjs, eventually, could be a JavaScript library, that permits the applied scientist to make an interesting and high playing UI Layer. React Native is a complete framework for building cross-platform apps, be it web, iOS or robot.
    In Reactjs, virtual DOM is employed to render browser code in Reactjs. In React Native, native arthropod genus are accustomed to render parts in mobile.
    The apps developed with Reactjs renders HTML in UI. React Native uses JSX for rendering UI, that is nothing however javascript.

18.What is the storage system in React Native?

Ans:

React Native uses AsyncStorage category to store information in key-value try that is international to any or all apps.

19.What are navigators?

Ans:

These are accustomed amendments from one scene to a different scene.

20.What is React Native?

Ans:

React Native could be a mobile app development framework that allows the event of multi-platform robot and iOS apps exploitation native UI parts.It is supported the JavaScriptCore runtime and Babel transformers.This renowned framework for mobile app development started within the summer of 2013 as Facebook’s internal hackathon project.

21.Tell America some choices of storing uninterrupted information in a very react native app?

Ans:

  • Async Storage (“built-in” to React Native)
  • SQLite
  • Realm
  • Firebase
  • MongoDB

22.What is Scrollview?

Ans:

It helps in viewing the massive content employing a scrollbar.

23.What are props in React Native?

Ans:

Props square measure parameters that square measure accustomed to customize an element at the time of creation and on re-render. Props square measure like arguments passed to a React element.

24.Can we have a tendency to mix native ios or golem code in React Native?

Ans:

Yes. iOS and golem are combined in React Native.

25.What is the employment of the XHR module in React Native?

Ans:

XHR HttpRequest is an associate degree API that is employed for implementation of HttpRequest so as to post information on a server.

26.How will React Native deal with a spread of screen sizes?

Ans:

Flexbox provides a uniform layout on screen with totally different sizes victimizing its 3 properties: justify-content, flex-direction, alignItems.Dimensions will vogue the page accurately on screen with totally different sizes.

27.What square measure animations? However, can they add React Native?

Ans:

Animations square measure artful pictures or objects that seem as moving objects. We will use animations with React Native API, Animated.decay, Animated.parallel and Animated.stagger.

28.How is React Native totally different from alternative frameworks for developing a mobile application?

Ans:

React Native app could be a real mobile app, not an internet app running within a mobile app shell. alternative different like Cordova, ionic run internet|an internet|an online} app in a very web read.React Native app is reborn into machine language that runs on mobile that’s why it provides higher performance than other alternatives.

29.Is there a browser IDE for react native?

Ans:

Yes, there is a square measure Browser IDE for React Native.

30.What is Flex?

Ans:

Flex or flex boxing could be a technique to distribute totally different parts in react native apps. you’ll be able to distribute react native views horizontally, vertically, give area in between or area around.

31.What determines the dimensions of an element and what square measures the ways?

Ans:

The height and dimension confirm the dimensions of the element on the screen. 2 other ways to line height and dimension:

  • Fixed Dimensions.
  • Flex Dimensions.

32.What is Render?

Ans:

Render Props could be a technique {in that|during which|within which} react parts square measure reworked into DOM nodes which square measure understood by the browser.

33.Will react native support html?

Ans:

React Native doesn’t support HTML.

34.What square measures the disadvantages of victimization React Native?

Ans:

React Native remains new and immature: React Native could be a new framework in Windows, Android, and iOS programming languages. it’s still within the improvement stage, which may have a negative impact on the apps.

35.What is Cross platform application development?

Ans:

Cross Platform Application Development could be a platform for making totally different computer code that square measure supported by multiple mobile in operation systems.

36.Why will React Native use Redux?

Ans:

Redux could be a standalone state management library that React Native uses to change information flow among associate degree apps.

37.How will React Native load information on Server?

Ans:

React Native consumes Fetch API to load information on the Server once required.

38.How are you able to improve the performance (load speed, rendering quality) of images?

Ans:

  • Server-side compression.
  • Third-party tools like Cloudinary.
  • Image caching.

39.What square measures the benefits of victimization React Native?

Ans:

Cross-Platform: It offers the power to “Write once and run everywhere.” It’s accustomed to produce apps for golem, iOS, and Windows platforms.

Performance: The code written in React Native is compiled into native code, Which permits it for all in operation systems to supply nearer native look and functions within the same approach on all platforms.

40.What square measure hybrid apps?

Ans:

Hybrid mobile apps square measure applications that square measure put in on a tool, a bit like the other app.Hybrid apps square measure deployed in a very native instrumentality that uses a mobile WebView object. Once the app is employed, this object displays the website due to the employment of net technologies (CSS, JavaScript, HTML).

41.How does one run a React Native app on Android?

Ans:

  • First, modify the USB Debugging choice within the Developer choices.
  • Plug the device via USB to the event machine.
  • Run adb devices command to visualize that the device is properly connected to ADB.

42.What is the distinction between controlled and uncontrolled components?

Ans:

If the worth displayed on UI by the element is set by type input, then it’s referred to as a controlled element. On the opposite facet, if the State determines the worth, then it’s referred to as an associate degree uncontrolled element.

43.What is Style?

Ans:

Style could be a core element employed in React Native. To make associate degree apps look fashionable, We have a tendency to use vogue Core elements to brighten it.

44.Why can we use wavy brace whereas mercantilism is used in some libraries?

Ans:

Curly braces square measure accustomed to importing tiny items from the library.

45.What is Flexbox?

Ans:

Flexbox is employed to grant an even layout on totally different screen sizes.

46.What square measure the opposite modules would like for react native navigation?

Ans:

  • React-native-gesture-handler.
  • React-native-reanimated.
  • React-native-screens.
  • React-native-safe-area-context.
  • React-navigation-stack.

47.What square measures the similarities between React and React Native?

Ans:

Both, React and React Native uses:

  • React Lifecycle ways.
  • React State and Props.
  • React parts.
  • Redux Library.

48.Who is the founding father of React Native?

Ans:

Jordan Walke (Facebook) is the founding father of React Native.

49.What were the key issues with the MVC framework?

Ans:

  • Applications were slow and inefficient.
  • There was Brobdingnagian memory wastage.
  • Because of circular dependencies, a sophisticated model was created around models and views.

50.How are you able to develop camera pictures in React Native?

Ans:

React Native Image Picker could be a module that helps you in choosing pictures from your library or directly from the camera.

51.What square measures the categories of knowledge that manage a component?

Ans:

Their square measures 2 varieties of knowledge that manage a component: props and state. props square measure set by the parent and that they square measure mounted throughout the period of time of a part. For knowledge that’s aiming to amend, we’ve to use state.

52.What square measure keys are used for in React Native?

Ans:

Keys square measure used for creating a part distinctive when an amendment.

53.What is the view?

Ans:

It is outlined as an instrumentality that supports layouts like some bit handling, flexbox and additional.

54.What will NPM stand for?

Ans:

NPM stands for Node Package Manager.

55.How will Virtual DOM add React Native?

Ans:

Diffing: Virtual DOM tree is updated, and React Native compares previous and gift versions of Virtual DOM. This is often referred to as diffing.

Updating Real DOM: Once diffing has been done, react native updates those changes solely in real DOM.

56.What is the purpose of StyleSheet.create() in React Native?

Ans:

In React Native, StyleSheet.create() send vogue|the design|the fashion} just once through the bridge to avoid passing new style objects and ensures that values square measure changeless and opaque.

57.Are React elements usable in React Native?

Ans:

Yes, React elements square measure employed in React Native.

58.How many threads run in React Native?

Ans:

React Native UI Thread (Main Thread): This thread is employed for the layout of the mobile app.

React Native JavaScript Thread: It’s a thread wherever our business logic can run. It means that JS thread could be a place wherever our JavaScript code is dead.

59.What square measure Refs used for in React Native?

Ans:

Refs offer you direct access to a DOM part or an element instance.

60.What will NPM do?

Ans:

NPM could be a line interface program. It installs the command interface in React Native.

61.What square measures the steps to make your 1st React Native Apps?

Ans:

First, to make native app: npm install -g create-react-native-app.

Create your 1st React Native App: create-react-native-app myFirstProject.

62.What is the state of an exceedingly React component?

Ans:

State is different aside from props by that we will modify a React part. React part’s state price changes within the life cycle of components, in contrast to props. We must always circuitously change the price of the react part. React framework offers the setState technique by means that the state of a part ought to be modified.

63.How does one tell React to create in production mode and what is going to do?

Ans:

Typically you’d use Webpack’s DefinePlugin technique to link NODE_ENV to production. this may strip out things like propType validation and additional warnings. It’s additionally an honest plan to change your code as a result of React uses Uglify’s dead-code elimination to strip out development solely code and comments, which can drastically scale back the scale of your bundle.

64.When would you like a category part over a useful component?

Ans:

A Class part is employed once a part has state and lifecycle, otherwise a useful part is employed.

65.Is React Native Open Source?

Ans:

Yes. React Native is an ASCII text file Mobile Network Application Framework.

66.What strategy would you employ to optimize an oversized list of things on FlatList?

Ans:

  • Use PureComponent on renderItem with bind ways.
  • Add keyExtractor property.
  • Add page number.
  • Define getItemLayout.

67.When does one use a TouchableHighlight?

Ans:

The TouchableHighlight will be used wherever you’d use a button or link online. The background of this part becomes dark on pressing it.

68.How does one re-render a FlatList?

Ans:

By exploiting extraData property on the FlatList part. By passing extraData= to FlatList we have a tendency to check that FlatList can re-render itself once the state.selected changes.

69.Do you fathom FlatList in React Native and its advantage over scrollview?

Ans:

FlatList could be a part accustomed to showing a line of knowledge. FlatList is commonly accustomed to show long lost knowledge wherever the amount of things might fluctuate. It renders solely the part focused on the screen, not the total list, therefore it’s better to use FlatList instead of scrollview.

70.Have you detected Listview?

Ans:

It includes an inventory of things that square measure displayed in an exceedingly scrollable vertical list. It’s a core React native part.

71.What is Axios in React Native?

Ans:

With the assistance of Axios, the user will send GET, POST, PUT, and DELETE requests to the remainder API and render a response to the application.

72.Why are animations terribly clear and vital in React Native?

Ans:

The animated API of Native React is intended to be serialized. meaning users will send animation to native while not having to travel through the bridge on each frame. Once the animation gets started, the JS thread is going to be blocked, and therefore the animation can run swish.

73.How are you able to keep animations from being blocked on the JavaScript thread? Describe however this works and make a case for a number of the restrictions?

Ans:

  • By adding useNativeDriver faithful the animation choices.
  • It works by passing the animation to the native thread wherever it’ll not be blocked by the JavaScript thread.
  • This will work on non-layout properties like opacity and rework, however won’t work on things like flex, or position.

74.What is a fraction and why would you employ one?

Ans:

  • A fragment could be a means of grouping JSX components along while not adding to the render tree by wrapping them in an extra read.
  • A good example of wherever to use a fraction is in an exceedingly dedicated part of a screen wherever no extra instrumentality styling is required.

75.What is the employment of the ScrollView component?

Ans:

The ScrollView could be a generic scrolling instrumentality that may contain multiple elements and views. The scrollable things needn’t be uniform, and you’ll be able to scroll each vertically and horizontally.

76.Can you offer some ideas on a way to forestall memory leaks in your app?

Ans:

  • Release timers/listeners additional in componentDidMount.
  • Handle closure scope.

77.List the distinction between React Native and Xamarin?

Ans:

Using Xamarin, you’ll build iOS, golem Windows, and raincoat apps. meaning it’s a cross-platform framework, however it uses c# for development instead of javascript, in contrast to React native.

78.What is vogue Vs Stylesheet in React Native?

Ans:

    vogueStylesheet in React Native
    Style could be a set of attributes accustomed to the style of the UI as a part of the appliance. It consists of colors, strings, layouts, etc. The design in React Native is comparable to CSS in hypertext markup language.
    A stylesheet could be a cluster of designs. The design sheet is employed once it grows in size then its cleaner approach places all styles in a very single place.

79.When would you utilize ScrollView over FlatList or vice-versa?

Ans:

Do you have to render a listing of comparable things from AN array or the information is extremely big? Use FlatList.Do you have to render generic content in a very scrollable instrumentality and therefore the knowledge is small? Use ScrollView.

80.What will TouchableHighlight do?

Ans:

TouchableHighlighy could be a wrapper for creating views that respond properly to touches. On move, the opacity of the wrapped read is shriveled, which permits the underlay color to point out through, darkening or coloring the read. TouchableHighlight should have one kid.

81.How square measure Hot Reloading and Live Reloading in React Native different?

Ans:

  • Live reloading reloads or refreshes the whole app once a file changes.
  • Hot reloading solely refreshes the files that were modified while not losing the state of the app.

82.What is the employment of a React native packager?

Ans:

  • It is capable of translating the js code that your device has trouble understanding.
  • The conversion of a picture in AN object is completed by React native packager.

83.Which info is best for react native?

Ans:

SQLite info is best for react native.

84.Why is that the InteractionManager important?

Ans:

React Native has just one thread for creating UI updates which might be full and end in drop frames. Developers use interaction managers to make sure that the operation is merely dead once the animations occurred in order that any frame drops might not result.

85.What does one mean by component-driven development?

Ans:

The process of breaking the whole UI into numerous minor reusable elements and developing them alone. so building the entire UI by adding those severally engineered reusable elements. It results in quicker and strong development of applications. It ends up in less code, so less maintenance and fewer bugs to mend.

86.What is cloth in React Native?

Ans:

Fabric is that the new React Native design planned by the community to form the mobile application user expertise is shut or maybe higher than the native apps.

87.What square measure options of presentational/dumb components?

Ans:

  • Are involved with however things look.
  • Have markup and designs of their own.
  • Have no dependencies on the remainder of the app, like revived stores.
  • Don’t specify however the information is loaded or mutated.
  • Receive knowledge and callbacks completely via props.

88.What is meant by HOC in React Native?

Ans:

HOC could be a technique in React Native, that permits you to employ element logic. HOC takes an element, and offers back a new element.

89.What happens if you edit a module that solely exports React elements in quick Refresh?

Ans:

If you edit a module that solely exports React component(s), Quick Refresh can update the code just for that module, and re-render your element. You’ll edit something in this file, as well as designs, rendering logic, event handlers, or effects.

90.What is the Render Props Pattern?

Ans:

Render Props pattern is to share knowledge and practicality between elements while not continuance code. Besides sharing the information and practicality of the shared element, render props enabled developers to own the total management of the element rendering.

91.What are the three principles of the material design of React Native?

Ans:

  • Prioritizing the Tasks.
  • Immutable Shadow Tree.
  • Reducing Memory Consumption.

92.What are Smart/Container components?

Ans:

Smart elements keep track of state and concern with how things work. instrumentation element still receives information or operate via props and may pass it to a different sensible element or dumb element as props. The instrumentation element pattern is class-based and has constructor() functions.

93.Explain the re-architecture of React Native and also the importance of the changes?

Ans:

  • Facebook is functioning internally to vary the approach Javascript interfaces with Native Modules. This is often Associate in Nursing overhaul of the UI-Layer, it’s codenamed “Fabric”.
  • TurboModules are going to be an ensuing iteration of NativeModules. Significantly this can guarantee native modules are loaded thirstily rather than all quickly avoiding startup overhead.
  • Also, TurboModules may be referred to as synchronously avoiding asynchronous calls across the RN bridge.
  • Along with this alteration the core of React Native goes lean. Which implies several libraries like Async Storage, Geolocation and Device data are moving to separate repositories.

94.What JavaScript engine will React native use?

Ans:

In most cases, React Native can use JavaScriptCore, the JavaScript engine that powers expedition.

95.In quick Refresh, what is going to happen if you edit files foreign by modules outside of the React Tree?

Ans:

If you edit a file that’s foreign by modules outside of the React tree, quick Refresh can fall back to doing a full reload.

96.What is the Gesture answerer System?

Ans:

Gesture answerer System may be a system that manages the lifecycle of the applications that are inbuilt React- Native framework.

97.What ar Presentational/Dumb components?

Ans:

This element solely accountable to gift one thing to DOM. there’ll be no logic in the least within this element thus it’s referred to as dumb element. As a result of dumb element solely target the presentation, it’s ideally can the foremost reusable element.

98.What is meant by InteractionManager?

Ans:

InteractionManager is native module in react native, that helps animations run swimmingly in react native.

99.What is “Fast Refresh”?

Ans:

Fast Refresh may be a React Native feature that enables you to urge near-instant feedback for changes in your React parts. Quick Refresh is enabled by default, and you’ll toggle “Enable quick Refresh” within the React Native developer menu.

100.What happens if you edit a module wherever the exports aren’t React parts in quick Refresh?

Ans:

If you edit a module with exports that aren’t React parts, Quick Refresh can re-run each that module, and also the different modules commercialize it. Thus if each Button.js and Modal.js import Theme.js, redaction Theme.js can update each parts.

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