React Js Coding Interview Questions
Expertly Curated React Js Coding Interview Questions for Aspiring Developers
React Js coding interview questions are focused on testing the candidate's understanding of React Js concepts, ability to write efficient and optimized code, and problem-solving skills. These questions may cover topics such as components, state and props, JSX, handling events, lifecycle methods, styling, and debugging. It is important for candidates to have a thorough knowledge of React Js and practical experience in using it to develop applications in order to successfully crack a coding interview.
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1 - What is React and why is it popular?
React is a popular JavaScript library used for building user interfaces. It was developed by Facebook in 2011 and quickly gained popularity due to its ease of use, flexibility, and reusability. React uses a virtual DOM (Document Object Model), which makes updating and rendering data more efficient. It is also based on a component-based architecture, making it easier to manage complex UIs.
2) What are the advantages of using React?
Some advantages of using React include its ability to improve performance, scalability, and maintainability of applications. It also allows for code reusability, efficient data handling, and better organization of code.
3) What is the difference between a class component and a functional component in React?
A class component is declared using ES6 class syntax and has access to lifecycle methods, state, and props, whereas a functional component is declared as a JavaScript function and does not have access to these features. Class components are typically used for complex UI logic or state management, while functional components are simpler and used for displaying static content.
4) What is JSX and how does it differ from HTML?
JSX is a syntax extension used in React to write markup and logic in the same file. It closely resembles HTML but is not actually HTML as it gets compiled into JavaScript. JSX allows for easy integration of JavaScript logic and dynamic data into UI components.
5) What is the purpose of props in React and how are they different from state?
Props (short for properties) are used for passing data from a parent component to a child component. They are read-only and cannot be modified within the child component. On the other hand, state is used for managing data within a component and can be updated using the setState() method.
6) What is the significance of the virtual DOM in React?
The virtual DOM is a representation of the actual DOM (the HTML document) in memory. When there is a change in the state of a component, React compares the virtual DOM with the actual DOM and only updates the necessary components, making the process more efficient and faster.
7) What is the purpose of the key prop in React?
The key prop is used to give React a way to uniquely identify child elements of an array. It helps improve the performance of list rendering and aids in differentiating between components that may look similar.
8) What is the difference between presentational components and container components?
Presentational components are responsible for the visual representation of data and contain minimal logic. Container components, on the other hand, handle the application logic, fetch data, and pass it down to the presentational components.
9) What is Redux and what problem does it solve?
Redux is a popular state management library used in React applications. It provides a centralized store for managing the application state and makes it easier to access, update, and share data across different components. It also solves the problem of prop drilling (passing props through multiple levels of components).
10) How do you optimize the performance of a React application?
Performance optimization in React can be achieved by using methods such as lazy loading components, implementing a virtualized list for long lists of data, and using shouldComponentUpdate or React.memo to prevent unnecessary re-renders. It is also important to avoid unnecessary state updates and use React developer tools to identify performance bottlenecks.
11) What are React Hooks and how do they differ from class components?
React Hooks are a feature introduced in React 16.8 that allow developers to use features like state and lifecycle methods in functional components. They differ from class components as they allow for easier management of components without the need for complex class syntax.
12) How do you handle errors in React?
Errors in React can be handled using the try-catch block or by using the componentDidCatch lifecycle method in class components. React also provides a ErrorBoundary component that can catch and handle errors in child components.
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13) What is a Higher Order Component (HOC) and how can it be useful in React?
A Higher Order Component is a function that takes in a component as an argument and returns an enhanced version of that component. It is used for code reuse and providing additional functionality to components without the need for code duplication.
14) What is the purpose of a Router in React?
A Router is used for implementing client-side routing in React applications. It helps in navigating between different components based on URLs and also allows for passing parameters to components.
15) How do you test React components?
There are multiple ways to test React components, including using libraries/frameworks like Jest and Enzyme, or by using the React Testing Library. Developers can write unit tests for individual components, integration tests for testing multiple components together, and end-to-end tests for testing the complete application flow.
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React Js Practical Interview Questions
