Table of Contents
Introduction:
React Native is a JavaScript-based mobile application framework created by Facebook that enables coders to use React with the native mobile platform to develop mobile applications for iOS and Android. It makes use of JavaScript, which is a widely-used programming language. Javascript can be used to create mobile applications that are genuinely “native” in terms of look and feel.
The primary benefit of React Native is that code can be written once and shared across both iOS and Android devices.
React is one of the most widely used JavaScript front-end frameworks today, and its popularity is growing. This JavaScript framework is used by over 8,000 firms, including large names like Facebook, Instagram, Airbnb, and others. Many organizations are on the lookout for skilled React developers. To get one of these jobs, you’ll need to ace your React Native interview.
Choose the finest course for you from the most highly regarded tutorials/institutions and boost your app development skills.
Here’s a list of compiled top 55 React Native interview questions and answers to aid your preparation and put you ahead of the competition.
Q1. What exactly is React?
Facebook created the React front-end JavaScript library in 2011.
It uses a component-based technique to create reusable user interface components.
It is used to build complex and interactive online and mobile user interfaces.
Although it was only open-sourced in 2015, it has one of the largest communities behind it.
Q2. What are the characteristics of React?
The following are some of React’s key characteristics:
- Instead of using the real DOM, it employs the virtual DOM.
- Server-side rendering is used.
- It maintains unidirectional data flow, also known as data binding.
Q3. Describe some of React’s most significant benefits.
The following are some of React’s key benefits:
- It improves the performance of the application.
- It is suitable for both client and server applications.
- The readability of code improves owing to JSX.
- Other frameworks such as Meteor, Angular, and others are easy to connect with React.
- Writing UI test cases has become been easier using React
Q4. What are React’s limitations?
The following are some of React’s limitations:
- React is a library, not an entire framework.
- It has a big library that takes some time to understand.
- It may be hard for inexperienced programmers to understand.
- Because it employs inline templating and JSX, the coding becomes more difficult.
Q5. What is State and how does it play a role in React Native?
The components are controlled by the state. The variable data can also be saved in the state. Because states are fluid, their values can change at any time.
Q6. Can we use react-native to integrate Android and iOS code?
Yes, we can use react-native to combine Android and iOS code. React Native helps in the seamless integration of components written in Java, Objective-C, or Swift.
Q7. What is JSX?
JSX is an abbreviation for JavaScript XML. This is a React-specific file that combines the expressiveness of JavaScript with HTML-like template syntax. This makes the HTML file quite simple to understand.
Q8. What exactly do you mean when you say “virtual DOM”? Explain its operation.
A virtual DOM is a small JavaScript object that is a copy of the real DOM. It’s a node tree in which the elements, their characteristics, and content are listed as Objects and their properties. The render method in React produces a node tree from React components. It then updates this tree in response to data model mutations induced by the user’s actions or system.
This Virtual DOM is used in three simple steps.
- The entire UI is re-rendered in Virtual DOM representation whenever any source data changes.
The difference between the old and the new DOM representations is then calculated.
After the calculations are done, the real DOM will be updated to reflect only the changes that occurred.
2. The difference between the old and the new DOM representations is then calculated.
After the calculations are done, the real DOM will be updated to reflect only the changes that occurred.
3. After the calculations are done, the real DOM will be updated to reflect only the changes that occurred.
Q9. Why are browsers unable to read JSX?
Only JavaScript objects can be read by browsers, however, JSX is not a standard JavaScript object. To enable a browser to read JSX, we must first convert the JSX file into a JavaScript object using JSX transformers such as Babel, and then pass it to the browser.
Q10. Is React Native considered a mobile application?
Yes, React Native fulfils all of the requirements for a native mobile app built with native app components. It’s neither a mobile web app nor a hybrid mobile app that successfully runs an HTML5 app thanks to WebView. It creates a true mobile app that is indistinguishable from those built using Java or Objective-C.
Q11. In react native, what do you mean by dispatch?
The Redux store has a feature called dispatch. You dial the number for the store. to send a message. This is the only method to bring about a kingdom transformation. Your components never have immediate access to the store with React-Redux – connect does it for you.
Q12. What exactly are props?
Props are React’s acronym for Properties. They are read-only components that must be kept constant and pure. Throughout the programme, they are always passed down from the parent to the child components. A prop can never be sent back to the parent component by a child component. This helps in the maintenance of unidirectional data flow and is often used to display constantly generated data.
Q13. What is a React state and how does it work?
React components are made using states. States act as a data source and must be kept as simple as possible. In a nutshell, states are the objects that determine how components are rendered and behave. They, unlike the props, are malleable and produce dynamic and interactive elements.
Q14. What is the function of React’s render() method?
Render() is required for every React component. It returns a single React element that is the native DOM component’s representation. If more than one HTML element is to be rendered, they must be included within a single enclosing tag, such as etc. This function must be kept pure, that is, it must consistently return the same result.
Q15. In react native, what is fabric?
Fabric is the most recent React Native architecture proposed by the firm to design mobile apps with a closer and better user experience than native apps
Q16. What are React’s synthetic events?
Synthetic events are objects which contain the browser’s native event in a cross-browser wrapper. They combine the features of various browsers into a single API. This is done to ensure that the properties of the events are uniform across browsers.
Q17. What do you mean when you say “refs” in React?
References in React are abbreviated as Refs. It’s an element that allows you to save a reference to a certain React element or component, which will be returned by the render configuration function of the component. It’s used to get references to a certain element or component that render returned (). They’re useful when we need to make DOM measurements or add methods to components.
Q18. List some of the instances in which Refs should be used.
The following are examples of when references should be used:
- Select text or media playback when you need to manage focus.
- to activate required animations
- Third-party DOM libraries can be integrated.
Q19. In React, how do you modularize code?
The export and import properties can be used to modularize code. They facilitate in separating the components into separate files.
Q20. In React, how are forms created?
Forms in React are similar to those in HTML. However, with React, the state is saved in the component’s state property and can only be modified using setState (). As a result, the elements can’t update their state directly, thus a JavaScript function handles their submission. This function has complete access to the information that a user enters into a form.
Q21. What do you understand by Higher Order Components(HOC)?
Higher Order Component is a more extensive method of reusing component logic. It’s a pattern built from React’s compositional nature. HOCs are customized components that contain another component. They can accept any dynamically provided child component, but they will not change or replicate the behaviour of their input components. HOC can be defined as ‘pure’ components.
Q22. What can HOC be used for?
HOC can be used for a variety of activities, including
- Bootstrap abstraction, logic, and code reuse
- Render jacking at a high-level
- Manipulation and abstraction of states
- Manipulation of objects
Q23. What do you mean by “pure components”?
Pure components are the simplest and most swiftly written components. They can be used to replace any component that has only a render (). These components improve the code’s simplicity as well as the application’s performance.
Q24. What is the significance of keys in React?
Keys are used to distinguishing between different Virtual DOM Elements and the data that powers the UI. They assist React in optimising rendering by recycling all existing DOM elements. These keys must be a unique numeric or string, and React will only reorder the elements rather than re-rendering them if you use them. As a result, the application’s performance improves.
Q25. What were the most serious issues with the MVC framework?
The following are some of the most serious issues with the MVC framework:
- Manipulation of the DOM was quite costly.
- The applications were sluggish and ineffective.
- There was a lot of wasted RAM.
- A sophisticated model was built around models and views due to circular relationships.
Q26. Describe Flux.
Flux is an architectural design that enforces data flow in only one way. It uses a central Store, which has authority over all data, to control derived data and permit communication across numerous components. Any data updates throughout the application must happen only here. Flux enhances the application’s stability and reduces run-time errors.
Q27. What exactly is Redux?
Redux is one of the most famous front-end programming libraries. It is a state container for JavaScript applications that are used to handle the entire state of the application. Redux applications are simple to test and can run in a range of circumstances with consistent behaviour.
Q28. What are Redux’s three guiding principles?
- The primary source of truth: An object/state tree stores the entire application’s state within a single store. The single state tree simplifies debugging and inspecting the application as well as keeping track of changes over time.
- The state is read-only: Triggering an action is the sole way to change the state. An action is a basic JS object that describes a change. The action is the minimal representation of the change to that data, just as the state is the simplest representation of data.
- Pure functions make changes: Pure functions are required to specify how the state tree is transformed by actions. Pure functions are those whose return value is solely determined by the arguments’ values.
Q29. What exactly do you mean when by “Single source of truth”?
The ‘Store’ function in Redux is used to store the application’s complete state in one place. As a result, all of the component’s state is saved in the Store, and they receive changes directly from the Store. The single state tree simplifies debugging and inspecting the application as well as keeping track of changes over time.
Q30. Make a list of Redux’s components.
Redux is made up of the following elements:
- Action – An object that defines what happened is called an action.
- Reducer – This is where you’ll figure out how the state will change.
- Store – The complete application’s state/object tree is stored.
- View – This item just shows the data that the Store has provided.
Q31. Demonstrate how Data moves through Redux?
Q32. In Redux, how are actions defined?
In React, actions must have a type property that specifies the type of ACTION that is being performed. They must be specified as a string constant, and you can expand it with other properties. Action Creators are functions in Redux that are used to create actions.
Q33. Describe the function of Reducer.
Reducers are pure functions that describe how the state of the application changes in response to an ACTION. Reducers function by taking the previous state and action and returning a new state. Based on the type of activity, it determines what type of update is required and then returns new values. If no work has to be done, it returns to the previous state.
Q34. What is React Router and how does it work?
React Router is a strong routing library that is built on top of React making it simpler in adding new screens and flows to the application. This maintains the URL up to date with the data from a web page. It’s used to create single-page web apps since it has a consistent structure and behaviour. React Router offers a simple API.
Q35. What are the benefits of using Redux?
The following are some of Redux’s benefits:
- Predictability of output — Because there is just one source of truth, the store, there is no misunderstanding about how to sync the current state with actions and other portions of the app.
- Maintainability — With a predictable result and rigid structure, the code becomes easier to maintain.
- Client-side rendering — All you have to do is pass the store that was produced on the server to the client. This is particularly important for the initial render and improves the user experience by improving application performance.
- Developer tools — From actions to state changes, developers can keep records of everything that is occurring in the app in real-time.
- Community and Ecosystem – Redux has a large community and environment behind it, which makes it even more appealing to utilise. A large group of talented people contribute to the library’s improvement and development of numerous applications.
- Ease of testing — Redux’s code is mostly made up of simple, pure, and isolated functions. As a result, the code is tested and independent.
- Organisation – Redux is very particular about how code should be organised, which makes it more consistent and easier to work with when a team is working on it.
Q36. What is the purpose of the switch keyword in React Router v4?
Although inside the Router, a <div> is utilised to encapsulate many routes. When you only want a single route to be rendered out of the numerous defined routes, the ‘switch’ keyword is used. When the <switch> tag is used, it matches the typed URL to the defined routes in order.
Q37. In React, why do we need a Router?
A Router is used to define many routes, and when a user types a specific URL, the user is redirected to that route if the URL matches the path of any ‘route’ set inside the router. So, we need to add a Router module to our application that allows us to create many routes, each of which leads to a different view.
Q38. Make a list of key points to consider before integrating React Native into an existing Android app
The following are the main points to remember while integrating React Native components into your Android app:
- Create a directory structure with React Native dependencies.
- JavaScript is used to create React Native components.
- In your Android app, add a ReactRootView. The container for your React Native component will be this view.
- Run your native app while the React Native server is up and running.
- Finally, we must ensure that the React Native aspect of your application performs as planned.
Q39. How is the entire React Native code processed so that the final output can be displayed on a mobile device?
- The main thread starts execution and begins loading JS bundles when the app is first loaded.
- When JavaScript code is successfully loaded, the main thread transmits it to another JS thread so that when JS performs any heavy calculations, the UI thread is not affected.
- Reconciler starts “diffing” when React starts rendering, and it sends changes to another thread when it creates a new virtual DOM(layout) (Shadow thread).
- The layout is calculated by the shadow thread, which then delivers the layout parameters/objects to the main(UI) thread. we term it “shadow” here because it generates shadow notes.
- Since only the main thread can render something on the screen, the shadow thread should transmit the created layout to the main thread, and only then should the UI be rendered.
Q40. What are the main features of FlatList components?
In a scrollable list, the FlatList component displays similarly formatted data. It works effectively with huge data sets when the number of items in the list may change over time.
Key Features:
The FlatList only presents the rendered elements that are now visible on the screen, not all the elements listed.
Q41. What are the different types of Touchable components in React Native, and when should you utilise each one?
- Touchable components can identify and respond to tapping gestures.
- Touchable Components are the best choice depending on the type of input you wish to give.
- TouchableHighlight is used almost anywhere on the site where a button or link would be. When the user presses down on the button, the view’s background will become darkened.
- On Android, we can use TouchableNativeFeedback to show ink surface reaction ripples that react to the user’s touch.
- By reducing the opacity of the button and enabling the backdrop to be seen through when the user presses down, TouchableOpacity can be utilised to provide feedback.
Q42. What’s the real reason for React Native’s performance issues?
The actual reason for React Native’s slow performance is that each thread (Native and JS threads) is lightning fast. When you send components from one thread to another unnecessarily or more than once in a React Native project, you create a performance bottleneck. In React Native, a good rule of thumb is to avoid any kind of performance issue.
- Native thread for Java, Kotlin, Swift, and Objective C.
- The primary thread that performs everything from javascript-based animations to other UI components is the Javascript thread.
- The bridge, as the name implies, serves as a communication link between the native and JS threads.
Q43. Explain React Native’s async storage?
- Async Storage is the React Native equivalent of web-based Local Storage.
- Async Storage is a community-maintained React Native library that provides a key-value store that is asynchronous and unencrypted. Each app runs in its own sandbox, with no access to data from other apps, and Async Storage is not shared between them.
Q44. What distinguishes React Router from traditional routing?
| TOPIC | OLD ROUTING | ROUTING IN REACT |
|
INVOLVED PAGES |
A fresh file corresponds to each view. |
There is only one HTML page involved. |
|
WEBSITE URL CHANGES |
A server receives an HTTP request and responds with an HTML page. |
The only thing that has changed is the History attribute. |
|
FEEL |
Each view requires the user to navigate across multiple pages. |
The user is fooled into believing he is navigating between pages. |
Q45. What are the benefits of using React Native?
There are lots of benefits to using React Native, including a:
- Large Community.
Since React Native is an open-source framework with a strong community behind it, any problems can be handled by seeking online assistance from other developers.
- Reusability
Since no separate teams are required to support both platforms, code can be written once and used for both IOS and ANDROID, which helps in the maintenance and debugging of large complex apps, as well as reducing prices.
- Live and Hot Reloading
When a file changes, live reloading reloads or refreshes the entire app. If you were four links into your navigation and saved a change, for example, live reloading would restart the application and return it to the initial route.
Hot reloading only refreshes the updated files without changing the app’s state. For example, if you were four links into your navigation and saved a change to some styling, the state would not change, but the new styles would appear on the page without requiring you to return to the previous page because you would still be on the same page.
- Plugins from third parties
If the existing modules in React Native do not fulfil the business requirement, Third Party plugins can be used to help speed up the development process.
Q46. In general, what are threads? and what are the different threads in ReactNative and how do you use them?
The single sequential flow of control in a programme is controlled by a thread.
React Native currently uses three threads:
- MAIN/UI Thread – This is your Android/iOS app’s main application thread. The main thread has access to the application’s user interface and can update it.
- Shadow Thread – This can calculate layouts built using the React library in React Native, and it is a background thread.
- JavaScript Thread – This thread executes the main Javascript code.
Q47. What’s the difference between React and Angular?
| TOPIC | REACT | ANGULAR |
| 1. ARCHITECTURE | MVC is the only view available. | MVC Complete |
| 2. RENDERING | Rendering on a server | Rendering on the client’s computer |
| 3. DOM | The virtual DOM is used | RealDOM is used. |
| 4. DATA BINDING | Data bind only one way | Data bind both ways |
| 5. DEBUGGING | debugging during compile time | Debugging during runtime |
| 6. AUTHOR |
Q48. Distinguish between states and props.
| Conditions | State | Props |
| 1. Get the parent component’s initial value | Yes | No |
| 2. The value of the parent component can be changed | No | Yes |
| 3. set default values inside the component. | Yes | Yes |
| 4. Internal component changes | Yes | No |
| 5. Set the child components with a value | Yes | Yes |
| 6. Modifications in child components | No | Yes |
Q49. Distinguish between components that are stateful and those that are stateless.
| Stateful Components | Stateless Components |
| 1. Keeps a record of when a component’s state changes in memory. | 1. Calculates the components’ internal state. |
| 2. Have the power to amend the state | 2. don’t have the power to amend the state. |
| 3. Consists of information about past, current, and possible state changes. | 3. Has no information of previous, current, or possibly future state changes. |
| 4. Stateless components are notified of the state change requirement, and the props are sent down to them. | 4. They treat the properties received from the Stateful components as callback functions. |
Q50. What are the phases of the lifecycle of a React component?
The lifecycle of a React component is divided into three stages:
- The Initial rendering phase: The component is set to begin its life journey and find its way to the DOM.
- The phase of updating: After the component is added to the DOM, it can only update and re-render when a prop or state changes. This occurs only at this stage.
- The unmounting phase: The component is destroyed and deleted from the DOM during this phase of its life cycle.
Q51. Describe the React component’s lifecycle functions in detail.
Some of the most essential lifecycle methods are as follows:
- componentWillMount() – This method is executed right before rendering on both the client and server sides.
- componentDidMount() – Only executed after the first render on the client-side.
- componentWillReceiveProps() – Called as soon as the props from the parent class are received and before another render.
- shouldComponentUpdate() – Based on certain criteria, returns a true or false value. Return true if you want your component to update; otherwise, return false. It returns false by default.
- componentWillUpdate() — This method is called just before the DOM is rendered.
- componentDidUpdate() – Called as soon as the rendering is complete.
- componentWillUnmount() – This method is called after the component has been unmounted from the DOM. Its function is to free up memory space.
Q52. In React, what is an event?
Events in React are the triggered reactions to certain actions such as mouse hover, mouse click, keypress, and so on. Taking care of these events is comparable to taking care of events in DOM elements. However, there are certain syntactical distinctions, such as:
- Instead of utilising lowercase, a camel case is used to name events.
- Instead of strings, events are passed as functions.
The event argument specifies a set of properties that are unique to that event. Each type of event has its own set of characteristics.
Each event type has its own set of characteristics and behaviours that can only be accessed through the event handler.
Q53. In react native, what are hooks?
Hooks are a brand-new feature in React native. They make it feasible to use the state and other react features without having to use the class. The primary goal of using hooks is to deal with side effects in react’s functional components.
Q54. List some of the situations in which you should use Refs.
The following are examples of when references should be used:
- Select text or media playback when you need to manage focus.
- To start mandatory animations
- Third-party DOM libraries can be integrated.
Q55. In React, what is the difference between a component and an element?
- React Component: A class or method that accepts inputs and uses JSX to return a React element.
- React Element: It explains what the user wants to see on the screen. To put it another way, the react element is an object that represents some user interface.
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Learning Advantages:
- Learn about React Native’s core concepts including props, styling, flexbox, and more.
- Learn about the Activity Indicator, Status Bar, and other components and APIs.
- Configure the Header Bar and process the React Native Navigation.
- Create a Tab Navigation and insert an icon at the bottom of it.
- Create Material Top Navigator and Material Bottom Navigation.
- Learn everything about Asyncstorage and its techniques.
- Understand React Native’s Geolocation and Third-Party Libraries.
Career Advantages
- Become qualified for jobs as a React Native Developer, which require a strong background.
- Fill the thousands of vacant high-paying positions in industries where there is a talent shortage.
- Become an accomplished React Native Developer.
- Learn about the numerous learning opportunities and possibilities of Native React
- Make well-informed options when it comes to IOS and Android app development.
- Make well-informed options when it comes to IOS and Android app development.
- set yourself apart from your competitors during job interviews.
- Earn a Lucrative React Native Developer Certification
- Optimize your CV and LinkedIn profile with Professional growth.
Conclusion:
Congratulations! You’ve made it to the very bottom of the page. It will take some time to prepare for your React interview, so be patient. Prepare to practise, practise, and practise some more. There’s still so much more to discover about React.
The following are some of the finest techniques to keep learning:
- Getting some practical experience
- Practising your interview skills
- Starting to focus on React’s recommended practises
Check out for Front-End Developers courses online to discover more about what it takes to be a React Developer. You’ll learn all of the React foundations you need to know, as well as how to combine React with Firebase, utilise React Tracked to create a small web app, and much more in this hands-on learning route. By the end of the course, you’ll know how to use React to create amazing apps.
Good Luck!
Also Check this Video
FAQs:
Q1. Is react-native a good career option?It’s an excellent decision to start working for the company as a web developer, freelancer, or remote worker. Since React Native Web is the only and best way to build any website, the developer’s requirement is the same. It’s almost a trend that new technology increases market demand.
Learning React JS is an excellent place to start because it is incredibly popular among web developers all around the world. React (also known as React.js or React JS) is a free and open-source front-end JavaScript toolkit for creating user interfaces and UI components.
Learning React Native will take you from 1 to 12 months.
Requirements:
* 2+ years of professional React Native experience is required.
* Professional software development experience of at least 4 years is required.
* Working knowledge of Swift, Objective C, and Java is preferred but not essential.
* Experience in working with large, complex systems.
* Capability to take complete ownership of your work.
In India, the average react native developer salary is 816,668 INR per year or 419 INR per hour. Starting salaries for entry-level positions start at 500,000 INR per year, with most experienced professionals earning up to 1,761,250 INR per year.
Q6. What are the best sites for React Native course?The following are some of the best institutions for the courses mentioned above:
Henry Harvin Coding Academy
Udemy
Coursera
FreeCodeCamp
Reactjs.org (Official Website)
Pluralsight etc.
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