Interview Questions Of React Js

Web Design and Development

Interview Questions Of React Js

Interview Questions for React JS

Interview questions for React Js focus on assessing the candidate's understanding and knowledge of the React JavaScript library. These questions usually cover topics such as React components, JSX syntax, Virtual DOM, state and props, lifecycle methods, and handling events. Interviewers may also ask about the difference between React and other JavaScript frameworks, performance optimization techniques, and commonly used libraries in conjunction with React. These questions provide valuable insights into a candidate's experience and proficiency in using React for building user interfaces and web applications.

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1 - Explain what is React JS?

React JS is an open-source front-end JavaScript library used to create reusable and highly efficient user interfaces (UI) for web and mobile applications. It was developed by Facebook and has become increasingly popular in recent years due to its component-based architecture and high performance.

2) What is the benefit of using React JS?

React JS uses a virtual DOM, which makes it highly efficient and provides a better user experience by reducing page loading time. It also allows developers to create reusable components, making the development process faster and more manageable. It also has a large and active community, making it easier to find resources and solutions to any issues that may arise during development.

3) What is JSX in React JS?

JSX (JavaScript Extension) is a syntax extension used in React JS to write HTML-like code inside JavaScript. It makes writing React components more intuitive and readable, as well as providing a way to dynamically render HTML elements.

4) What are the components in React JS?

A React component is a reusable piece of code that specifies how a particular element should be displayed on the UI. Components can be either class components or functional components, and they can also have state and lifecycle methods.

5) What is the difference between a class component and a functional component in React JS?

A class component is a JavaScript class that extends the base React Component class. It has its own state and lifecycle methods, making it more suitable for complex UI elements. On the other hand, functional components are simpler and written as functions, making them faster and easier to write.

6) How does data flow in React JS?

React JS follows a one-way data flow from parent components to child components. This means that data can only be passed from top to bottom, and any change in the parent component will be reflected in its child components. This makes it easier to debug and manage application state.

7) What are props in React JS?

Props (short for properties) are used to pass data from a parent component to a child component. They are immutable and are read-only by the child component, meaning they cannot be modified by the child.

8) What is state in React JS?

State is a way to store and manage data within a component. It is mutable and can be modified using the setState() method. When the state is updated, the component will re-render, reflecting the changes in the UI.

9) What are the lifecycle methods in React JS?

React JS has three main lifecycle methods: mounting, updating, and unmounting. These methods are invoked at specific stages of a component's lifecycle and can be used to perform actions such as fetching data, updating the DOM, or cleaning up resources.

10) What is the purpose of the render() method in React JS?

The render() method is responsible for rendering the JSX (HTML-like code) of a component onto the DOM. It is a mandatory method in class components and is invoked whenever the component state or props are updated.

11) How does React JS handle error boundaries?

Error boundaries are React components that catch JavaScript errors anywhere in their child component tree and display a fallback UI instead of crashing the whole application. They are defined by the componentDidCatch() method and can be used to handle errors gracefully.

12) What are Higher Order Components (HOCs) in React JS?

Higher Order Components (HOCs) are functions that take in a component as an argument and return an enhanced version of that component. They are used to share common functionality between components and reduce code duplication.

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13) What is a Redux store in React JS?

Redux is a state management library for React JS that allows you to store, access, and update the overall state of your application in a centralized place. The Redux store acts as a single source of truth and can be accessed by any component in the application.

14) What are Pure Components in React JS?

Pure Components are a type of React component that performs a shallow comparison of their props and state to determine if a re-render is necessary. This can help improve performance, as only components with changed props or state will re-render.

15) How does React JS handle user inputs?

React JS uses event handling to handle user inputs. Event handlers are passed as props to the component and are invoked when a specific event, such as a click or input change, occurs. The handler function can then update the component state, which will trigger a re-render.


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