React Native interview questions and answers in 2022

This is one of the most asked React Native interview questions. Facebook created the React Native JavaScript framework to accommodate the growing demand for mobile app development. It's free and open-source, and it's built on JavaScript. Facebook developed ReactJS as well. It's an open-source JavaScript library for creating mobile and web applications with responsive user interfaces.

Let's look at some of the significant distinctions between them:

• Both React Native and ReactJS employ JSX, but only ReactJS uses HTML tags, whereas React Native does not.

• ReactJS employs a react-router, but React Native has its own built-in navigation module.

• ReactJS makes advantage of CSS animations. Its animation API is used by React Native.

• ReactJS makes use of a virtual DOM that only refreshes partially. When rendering UI components, React Native must use its native API.

• ReactJS is primarily used for web app development, whereas React Native is primarily utilized for mobile app development.

A component is a fundamental building block in React. In other words, every application you create in React will be made up of pieces known as components. Components make it much easier to create user interfaces. You can see a UI broken down into multiple individual components and work on them independently before combining them all in a parent component, which will be your final UI.

They are of 2 types:

• Functional Components: Javascript functions are used to create functional components. By writing a javascript function, we can create a functional component in React.

• Class Components: Class components are slightly more complicated than functional components. The functional components in your program are unaware of the other components in your program, whereas the class components can collaborate. Data can be passed from one class component to another.

This is a popular React Native interview question. Redux is a JavaScript application state management tool. It enables you to develop apps that are consistent, adaptable to multiple situations, and simple to test.

Redux isn't required for all applications. Its purpose is to assist you in determining when your state changes. Here are some examples of when you would wish to use Redux, according to the official Redux documentation:

• Your app's status is often changed.
• You have a lot of app states, and it's used in a lot of locations throughout the app.
• The reasoning for updating the state of your program is convoluted.
• You'd like to see how the state has changed throughout time.
• Your app's codebase is medium or huge, and it will be worked on by several people.

The Virtual DOM in React Native is a duplicate of the real DOM. It's a node tree that shows the attributions, contents, and properties of elements. The Virtual DOM will re-render the UI if our underlying data changes. The discrepancies between other DOM representations and Virtual DOM representations will then be counted, and the real DOM will be updated as a result.

All of React's main components accept a style prop. This prop can be a straightforward JavaScript object. You can also pass a collection of distinct styles.

If your components are complicated, it is best to utilize StyleSheet.create to build several styles in one place.

Higher-order components are pure functions that take input and output fresh input. Their primary function is to condense and reuse stateful logic across several components. They are considered advanced approaches and are not included in the React API. Instead, they are patterns that emerge from the compositional structure of React.

This is a common React Native interview question. There are numerous approaches to optimizing an application. Let's have a look at some of the possibilities. We are able to:

• Instead of simply saving our raw JSON data, we need to compress or convert it.
• Reduce the size of APK files for CPU architectures.
• Optimize the number of state operations and native libraries.
• On list items, use key characteristics.
• Images and other graphic components should be compressed.
• Use Proguard to reduce app size by stripping parts of our bytecode and its dependencies.

React Native currently employs three threads:

MAIN/UI Thread – The main application thread on which your Android/iOS app runs. The main thread has access to the application's UI and can update it.

Shadow Thread — This is a background thread that can calculate layouts built with the React framework in React Native.

**JavaScript Thread **– This thread executes the primary Javascript code.

Timers are an essential component of any program and React Native implements browser timers.

setTimeout, and clearTimeout There may be business requirements to execute a specific piece of code after a specified amount of time or after a delay. In such circumstances, setTimeout can be used, while clearTimeout merely clears the timer that has been established.

clearInterval, setInterval setInterval is a method that invokes a function or executes code at defined time intervals, as provided by the second parameter. A function or block of code bound to an interval runs until it is terminated. The clearInterval() method can be used to end an interval.

setImmediate, clearImmediate The function or execution is called as soon as possible. clearImmediate is used to cancel the immediate actions defined by setImmediate ().

cancelAnimationFrame, requestAnimationFrame It is the most common approach to creating animations. A function is called to update an animation before the next animation frame.

This is a common react native interview question. Props Drilling (Threading) is a term that refers to the process of passing data from the parent component to the identical child component, although other components possess the props in between only to send it down the chain.