Top 10 Reactjs Interview Questions

React course will teach you how to create your own applications that can be used on your phone or on your computer or in any other place. Check out this article as it consists of frequently asked react js interview questions.

1.What is React?

ANS : React is an open-source JavaScript frontend library for creating user interfaces, particularly for single-page apps. It is used to manage the view layer in online and mobile applications. Jordan Walke, a Facebook software engineer, is the creator of React. React was originally used in 2011 on Facebook's News Feed and in 2012 on Instagram.

2.Explain the features of React?

ANS :The following are some of React's key features:

*Because RealDOM manipulations are costly, it uses VirtualDOM instead of RealDOM. *Server-side rendering is supported. *Follows data binding or unidirectional data flow. *The view is built using reusable/composable UI components.

3.Define state in React?

ANS :A component's state is an object that contains information that may change over the component's lifespan. We should always attempt to keep our state as basic as feasible, with as few stateful components as possible.

4.What are Props in React?

ANS :Props are components' inputs. They are single values or objects with a set of values that are supplied to components when they are created using a naming scheme similar to HTML-tag attributes. They're information passed from a parent component to a child component.

5.Differentiate state and props?

ANS : Props and state are both standard JavaScript objects. While they both contain information that determines render output, their functioning is distinct in terms of components. Props are supplied to the component in the same way those function parameters are passed to it, whereas the state is maintained within the component in the same way that variables specified within a function are managed.

6.Why should we not update the state directly?

ANS :If you try to update the state directly, the component will not re-render.

7.When to use a Class Component over a Function Component?

ANS :Use a class component if the component requires state or lifecycle methods; otherwise, use a function component. With the advent of Hooks in React 16.8, you may now leverage state, lifecycle methods, and other capabilities that were previously exclusively available in the class component in your function component.

8.What is JSX?

ANS :JSX is an ECMAScript syntax extension that is similar to XML (the acronym stands for JavaScript XML). It essentially serves as syntactic sugar for the React.createElement() function, allowing us to combine the expressiveness of JavaScript with HTML-style template syntax.

9.What is React Fibre?

ANS :In React v16, Fiber is a new reconciliation engine or reimplementation of the main algorithm. React Fiber's goal is to improve its applicability in areas such as animation, layout, gestures, the ability to halt, abort, or reuse work, and assign priority to different sorts of updates; and additional concurrency primitives.

10.Can you tell us about lifting the state up in React?

ANS :It is recommended to elevate the shared state up to their closest common ancestor when numerous components need to share the same dynamic data. That is, if two child components share the same data from their parent, instead of retaining local state in both of the child components, shift the state to the parent.

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