React Js Interview Questions For Senior Developer
Expert-Level React JS Interview Questions for Experienced Developers
React Js Interview Questions for Senior Developers often include questions about advanced concepts such as performance optimization, state management, code reusability, and project architecture. Senior Developers are expected to have a deep understanding of React principles, best practices, and common pitfalls. They should also be able to confidently articulate their thought process and decision-making skills, as well as discuss how they have successfully tackled complex challenges in previous projects. Strong communication, leadership, and collaboration skills are also valued in senior roles.
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1 - What is React JS and what are its main features?
React JS is a popular JavaScript library used to build user interfaces. It follows a component-based approach and allows developers to create reusable UI components. Some of its main features include virtual DOM, JSX syntax for HTML-like code, server-side rendering, and one-way data binding.
2) What is the significance of a virtual DOM in React JS?
Virtual DOM is a representation of the actual DOM in JavaScript, providing a fast and efficient way to update the DOM. React JS compares the virtual DOM with the actual DOM and only updates the specific elements that have changed, avoiding expensive DOM operations. This results in better performance and a smoother user experience.
3) How is server-side rendering beneficial in React JS?
Server-side rendering allows the initial content of a website to be loaded by the server and sent to the browser as a fully rendered page. This enables search engine crawlers to index the page, improves performance by reducing client-side rendering, and provides a better user experience for users with slower internet connections.
4) What is the difference between state and props in React JS?
State is an internal data storage mechanism of a component that is managed by React JS. It can be updated by the component itself, and changes to state trigger a re-render of the component. Props, on the other hand, are passed from a parent component to a child component and are immutable. They provide a way to pass data and communicate between components.
5) How can you optimize performance in React JS?
Performance can be optimized in React JS by implementing features such as server-side rendering, code splitting, and using React.memo() to prevent unnecessary re-renders. Additionally, using React's built-in tools like Profiler and shouldComponentUpdate can help identify and improve performance issues.
6) What are React Hooks and how do they differ from class components?
React Hooks are functions that allow developers to add state and lifecycle methods to functional components. Hooks provide an alternative to class components and enable developers to use local state and lifecycle methods without having to use class components. They also promote code reusability and help reduce the overall complexity of the codebase.
7) What is the role of Redux in React JS?
Redux is a popular state management library used in React JS applications. It provides a centralized store for application state and follows a unidirectional data flow pattern. This helps to manage complex applications with a large amount of data and enables components to access and update the state in a predictable manner.
8) Can you explain the concept of React Fragments?
React Fragments allow developers to wrap a list of elements without introducing an additional parent element into the DOM. This is especially useful when rendering multiple components without a parent container. Fragments appear as an empty tag in the DOM and help to keep the codebase clean and organized.
9) What are Higher-Order Components (HOC)?
Higher-Order Components (HOC) are functions that take in a component as an argument and return a new enhanced component. HOCs enable code reuse and help add functionalities like authentication and data fetching to multiple components without having to modify them. They are commonly used in React JS when implementing cross-cutting concerns.
10) How do you handle errors in React JS?
React JS provides a built-in Error Boundary component that catches JavaScript errors in the component tree below it. Developers can wrap parts of the application with the boundary component to handle errors gracefully and display a fallback UI. Additionally, libraries like Sentry can be used to track and log errors in React JS applications.
11) What are some best practices for writing efficient code in React JS?
To write efficient code in React JS, it is important to follow best practices such as using pure functions, avoiding unnecessary re-renders, using keys in lists, and implementing code splitting for better performance. It is also important to follow a modular approach, use appropriate naming conventions, and write readable and maintainable code.
12) Can you explain the concept of Flux in React JS?
Flux is an architectural pattern that complements the components and data flow of React JS. It provides a unidirectional data flow, where data flows in a single direction, and changes to the data are managed by a central store. This helps to prevent complex data flow patterns and ensures consistency across the application.
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13) How do you handle cross-site scripting (XSS) attacks in React JS?
React JS comes with built-in protection against cross-site scripting attacks. The library automatically escapes any user input before rendering it in the DOM, thus preventing malicious code from being injected. Developers can also use libraries such as DOMPurify to sanitize user input and prevent XSS attacks on their applications.
14) Can you explain the concept of portals in React JS?
Portals allow developers to render a component's children in a different DOM node, rather than the node where the component is currently being rendered. This is useful when a component needs to be rendered outside of its parent component, for example, in a modal or a tooltip. Portals provide a cleaner and more flexible way to manage DOM elements in React JS.
15) How do you debug a React JS application?
React JS provides built-in debugging tools like React Developer Tools, which can be installed as a browser extension. These tools help to inspect React component hierarchies and identify issues such as unnecessary re-renders. Additionally, the use of breakpoints, console.log, and React error boundaries can assist in debugging complex issues.
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