Introduction
React Native, crafted by Facebook, stands as an open-source JavaScript framework tailored for native mobile app development. Rooted in the JavaScript library React, it streamlines the creation process of genuine native mobile applications.
This framework boasts a significant advantage in time efficiency, allowing developers to construct fully functional native mobile apps using a singular language: JavaScript. This means that with React Native, you code once and seamlessly across both Android and iOS platforms. The resulting React Native app inherits the distinctive native appearance and behavior, ensuring a polished user experience.
Top Interview Questions & Answers Of React Native
1. What is React Native?
React Native is an open-source framework found by Facebook for constructing native mobile applications, incorporating JavaScript and React. It paves the way for developers to build native component-based cross-platform applications, providing a native-like user experience.
2. How Does React Native Vary From React?
React is a JavaScript library for creating user interfaces, mainly for web applications, while React Native is a framework for developing native mobile applications. React uses virtual DOM to render UI components, whereas React Native compiles JavaScript code into native code for each platform.
3. What are the benefits of using React Native while creating mobile apps?
- Cross-platform compatibility
- Native performance
- Reusable components
- Hot reloading for faster development
- Large ecosystem and community support
- Cost-effectiveness
4. How is cross-platform functionality accomplished using React Native?
The reason React Native is able to work on both Android and iOS is that it uses a single JavaScript codebase that is translated into native code for both platforms. Because of this, programmers may create code once and then share it with other platforms. This cross-platform capability is especially useful for applications like e-commerce order fulfillment, where consistent and reliable performance across devices is essential for managing orders and inventory efficiently. For example, when integrating features such as a virtual phone number system for customer support, React Native allows developers to implement this functionality seamlessly across different mobile platforms without needing separate codebases.
5. What is the purpose of JSX in React Native?
To define the user interface, React Native and React employ the JSX syntax extension. It simplifies the development of user interface components by letting developers write HTML-like code inside JavaScript.
6. Explain the concept of props in React Native.
The term “props” describes the method by which parent components in React Native may communicate with the child ones. They allow you to personalize and set up child components according to their parents’ requirements, and they’re not changeable.
7. Compared to hybrid applications, how are native apps different?
The main difference between native applications and hybrid apps is that the latter are made to work on several platforms, while the former are optimized for just one. Hybrid app development makes advantage of React Native.
Although hybrid applications tend to be less maintenance-intensive and quicker to design, they cannot quite live up to the performance of native apps.
8. What are state and setState in React Native?
In JavaScript, an element’s “state” is an object that holds its currently active data or status. To change a component’s state and trigger a re-render of the user interface according to the changed state, you may use the setState function offered by React Native.
9. What is the purpose of AsyncStorage in React Native?
AsyncStorage is a pre-built storage system in React Native used for storing and retrieving data on the device. It is commonly used for storing user preferences, authentication tokens, and other application data.
10. What system does React Native use for navigating between different screens?
Several navigation frameworks are available in React Native for managing screen-to-screen navigation, including React Navigation and React Native Navigation. By using these libraries, programmers may design the application’s navigation stacks, tabs, and drawers.
11. Give an overview of Redux and its advantages in React Native.
Applications built using React Native (or React) often make use of Redux, a tool for managing states. It simplifies the maintenance and debugging of complicated state logic by providing a single store to handle the application’s state. Redux makes it easy for components to communicate with one other and allows for predictable state management.
12. Can you explain the key distinctions between native development and React Native?
Instead of creating separate codebases for iOS and Android using their respective languages, developers may use React Native to create cross-platform apps using JavaScript and React.
13. Describe the function and significance of React Native bridges.
The communication between native code and JavaScript code is handled via React Native bridges. They let React Native apps use components and APIs that are particular to the platform. In order to optimize speed and integrate native features into React Native apps, it is essential to understand bridges.
14. Give an example of a React Native app’s architecture.
In a typical React Native project, bridges allow native modules to communicate with JavaScript code running on a JavaScript engine like JavaScriptCore. Rendering user interface elements and managing device features are handled by native modules through interactions with platform-specific APIs and components.
15. How does React Native Navigation vary from React Navigation? Which would you prefer, and when?
A native navigation library is React Native Navigation, while the one based on JavaScript is React Navigation. Although it needs more setup, React Native Navigation provides greater performance and a native feel. However, many prefer React Navigation because of its simplicity and cross-platform support.
16. How controlled and uncontrolled input vary in React.
When it comes to handling form data, controlled components use the React state, while uncontrolled components use the document object model (DOM).
Controlled components are usually the way to go since they streamline the form data management, validation, and submission processes by creating a central repository for all of the form data.
import React, { useReducer, useRef } from “react”;
// Controlled with useReducer
const ControlledInputForm = () => {
const [state, dispatch] = useReducer((_, action) => action.payload, “”);
return (
<form onSubmit={e => {e.preventDefault(); console.log(state);}}>
<input value={state} onChange={e => dispatch({ payload: e.target.value })} />
<button type=”submit”>Submit</button>
</form>
);
};
// Uncontrolled with FormData
const UncontrolledInputForm = () => {
const formRef = useRef();
return (
<form
ref={formRef}
onSubmit={e => {
e.preventDefault();
console.log(new FormData(formRef.current).get(“inputName”));
}}
>
<input name=”inputName” />
<button type=”submit”>Submit</button>
</form>
);
};
17. What is the virtual DOM? When rendering the user interface, how does react make use of the virtual DOM?
A library like ReactDOM keeps a memory-based copy of the document object model (DOM) in sync with the physical DOM, according to the React team’s definition of virtual DOM.
- When was virtual DOM first implemented?
Although document object model (DOM) manipulation is essential to any online application, it is somewhat sluggish in comparison to other JavaScript tasks. When several DOM operations are being performed, the application’s efficiency is compromised. To accommodate even minor DOM changes, the majority of JavaScript frameworks update the complete document object model (DOM).
Just think of a list being rendered inside the DOM as an example. Instead of merely presenting the altered or updated item, the full list is shown anew whenever an item in the list is altered or revised. It’s known as inefficient updating.
The React team came up with the idea of virtual DOM to fix the issue of inefficient updating.
- What is the process?
There is a virtual DOM object (copy) that corresponds to each DOM object and shares all of its characteristics. The primary distinction between a real DOM object and a virtual DOM object is that the latter does not immediately update the former in terms of how it appears on the screen. One way to think about a virtual DOM object is as a model of the actual DOM object. Rendering a JSX element updates all virtual DOM objects.
Despite what one might expect, it is not wasteful to update each virtual DOM object. Changing the virtual DOM is far quicker than changing the actual DOM because we are only changing the real DOM’s blueprint.
For UI rendering, React employs two virtual DOMs. You may use one to keep track of how things are right now, and the other to recall how they were in the past. React checks for changes to which virtual DOM objects whenever the virtual DOM is changed by comparing the two DOMs. Rather than rendering the entire actual DOM, react renders only the items that were modified, once it knows which ones. Using virtual DOM, React is able to address the issue of inefficient updating in this manner.
18. Give an overview of FlatList and VirtualizedList, and describe their functions in React Native.
When it comes to effectively rendering huge lists, React Native has you covered with components like FlatList and VirtualizedList. As a result of its more personalization possibilities, VirtualizedList is better suited to complicated lists with heterogeneous data and dynamic content, whereas FlatList is better suited to basic lists with homogeneous data.
19. How would you approach state management in a React Native application of large size?
Managing large-scale states, Redux, MobX, and the Context API are some of the libraries that may be used to manage React Native apps. To manage application state, ease data flow between parts and deliver predictable state management, these libraries offer centralized stores. This is particularly beneficial in complex enterprise applications like CRMs, where tracking user actions, notifications, or maintaining a sales pipeline demands highly consistent and scalable state logic across components.
20. Describe how to build native modules in React Native. Please give an example when creating a native module from scratch would be necessary.
In order to let JavaScript in React Native apps access native functionality, native module development necessitates developing platform-specific code, such as Java for Android or Objective-C/Swift for iOS. If you want to use platform-specific APIs (such sensors on devices or your own UI elements) but JavaScript doesn’t support them, you’ll need to create native modules.
21. In React, what are synthetic events?
One way to make sure that events work in every browser is to use synthetic events. These events integrate the response of many browsers’ native events into one API. Irrespective of the browser being used, the application remains constant.
const MyLink = () => {
const onClick = (event) => {
event.preventDefault();
console.log(“link clicked”);
};
return <a onClick={onClick}>Click me</a>;
};
22. Describe the difficulties of testing React Native apps and offer solutions.
Establishing testing environments, simulating native modules, dealing with asynchronous code, and testing user interface components on many platforms are all obstacles to overcome while testing React Native apps. Jest, Detox, and the React Native Testing Library are testing frameworks that can help with these issues, as can effective snapshot and mock testing procedures.
23. Give an overview of Hermes and JavaScriptCore in React Native, and explain when you can use each.
When compared to JavaScriptCore, Hermes, a React Native-optimized JavaScript engine, provides superior performance with a smaller memory footprint. While JavaScriptCore is still utilized for iOS apps and development/debugging, Hermes is more suited for commercial apps targeting Android devices.
24. In React, what does “prop drilling” mean? How can you avoid it?
Data passing between higher-level components and lower-level components is a common requirement when building React apps. The phrase “prop drilling” describes the procedure of moving props from an upper-level component to a lower-level component via all of the lower-level components.
The use of prop drilling has a number of drawbacks, including making code more difficult to maintain and granting access to components that shouldn’t have it. If you use the Context API or a State Management library, you could avoid prop drilling.
25. Explain React Hooks.
React Hooks are intrinsic methods that enable developers to utilize the lifecycle and state management of React components. These functions were introduced in the latest version of React, 16.8. Mount, unmount, and update are the three stages that make up a component’s lifetime. Components also possess qualities and can be in different states. As a result of hooks, developers will be able to utilize these methods to more easily traverse the component tree and improve code reuse.
You may use all of React’s functionality without building any class components by using Hooks. To manage a component’s state, for instance, you needed a class component prior to React version 16.8. However, one may now retain the state in a functional component by utilizing the useState hook.
26. Can Redux be substituted by React Hooks?
When it comes to handling the global application state tree for massive app structures, the React Hook is not an appropriate substitute for Redux. Redux is an open-source JavaScript library that helps with application state management. However, React does offer a useReducer hook that handles state transitions similarly to Redux. Rather than declaring several useState hooks, Redux is helpful at lower levels of component hierarchy for handling dependent components of a state.
The complexity of bigger commercial online apps is likely to be great; therefore, relying just on React Hooks might not be enough. A small number of developers will attempt to use React Hooks alone, while others will use a hybrid approach, combining React Hooks with Redux.
Conclusion
The world’s leading IT firms, particularly those based in India, are increasingly using React. This includes Facebook, PayPal, Instagram, Uber, and many more. React is quickly gaining popularity among the developers community due to the fact that they simplify state management and other processes.
As a resource for those preparing for interviews, this article compiles the most common interview questions and their corresponding answers pertaining to ReactJS and React Hooks. A positive attitude and solid first impression will go a long way toward determining how well you do in the interview, so keep that in mind as well.
