May 18, 2024

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Advanced ReactJS Interview Question & Answer

Discover the top advanced ReactJS interview questions and expert answers to ace your next ReactJS developer interview with confidence. For more, read this post.
Advanced ReactJS Interview Questions


ReactJS has revolutionized front-end development with its efficient and declarative approach to building user interfaces. Aspiring developers keen on mastering React are required to explore a myriad of concepts, from the fundamentals to the advanced. This guide provides detailed information on the prerequisites to be eligible for the Advanced ReactJS Interview round while delving into some of the important React JS Advanced Interview Questions and answers.

How To Become Eligible For Advanced ReactJS Interview?

To become eligible for advanced ReactJS interviews, it’s essential to have a strong foundation in React fundamentals. Additionally, one must gain knowledge with advanced concepts and practical experience.

Here’s a roadmap to becoming eligible:

  • Master the Fundamentals: Ensure you have a solid understanding of React basics, including components, JSX syntax, props, state, and lifecycle methods. Practice building simple applications to reinforce your understanding.
  • Learn Advanced Concepts: Dive deeper into advanced React topics such as Hooks, Context API, Portals, Error Boundaries, Higher Order Components (HOCs), and Render Props. Understand how these features work and when to use them effectively. You can join a React JS Course for the best guidance under expert mentorship.
  • Practice with Real-world Projects: Work on real-world projects to gain practical experience and apply what you’ve learned. Build applications of varying complexity, such as CRUD apps, e-commerce platforms, or social media clones, to demonstrate your skills.
  • Explore State Management: Familiarize yourself with state management libraries like Redux, MobX, or Recoil. Understand the principles of state management and how to efficiently manage application state in complex React applications.
  • Optimize Performance: Learn performance optimization techniques such as code-splitting, memoization, lazy loading, and minimizing re-renders. Understand the tools and techniques available for profiling and debugging React applications.
  • Stay Updated: React ecosystem evolves rapidly, so stay updated with the latest React features, best practices, and community trends. Follow React blogs, participate in forums, and contribute to open-source projects to stay abreast of developments.
  • Build a Strong Portfolio: Showcase your skills by creating a portfolio showcasing your React projects, contributions to open-source, and any relevant certifications or courses completed.

By mastering these aspects, you’ll be well-prepared to tackle advanced ReactJS interviews and demonstrate your expertise in building scalable and efficient React applications.

Advanced ReactJS Interview Questions And Answers

Let us now explore some of the most commonly asked React JS Advanced Interview Questionsalong with their suitable answers.

What are React Portals?

    React Portals provide a way to render children into a DOM node that exists outside the DOM hierarchy of the parent component. This allows rendering children components at a different DOM location than their parent.

    Explain the concept of Higher Order Components (HOC) in React.

    Higher Order Components are functions that take a component and return a new component with enhanced functionality. They enable code reuse, logic abstraction, and composition in React applications.

    What are hooks in React?

    React Hooks are functions that enable functional components to use state and lifecycle features that were previously only available in class components. Examples include useState, useEffect, useContext, etc.

    How does React handle forms?

    React manages form data using controlled components, where form elements like inputs, selects, and textareas are controlled by React state. This allows React to handle form submission and validation efficiently.

    What is the purpose of React Context?

    React Context provides a way to pass data through the component tree without having to pass props down manually at every level. It’s useful for sharing data that is considered global within a React application.

    Explain the Virtual DOM in React.

    The Virtual DOM is a lightweight copy of the actual DOM. React uses it to improve performance by minimizing direct DOM manipulation. When state changes occur, React reconciles the Virtual DOM with the real DOM to efficiently update only the necessary parts.

    What is the significance of key prop in React lists?

    The key prop is a special attribute used by React to identify which items have changed, been added, or been removed from a list. It helps React efficiently update the UI when the list changes.

    What are the differences between componentWillMount and componentDidMount?

    componentWillMount is invoked just before mounting occurs, while componentDidMount is invoked immediately after the component is mounted. In most cases, you should use componentDidMount for API calls and other side effects.

    How do you handle code-splitting in React?

    Code-splitting is achieved in React using dynamic import() syntax or React.lazy() and Suspense. This allows splitting the bundle into smaller chunks, which are loaded on-demand, improving performance by reducing initial load time.

    Explain the concept of lazy loading in React.

      Lazy loading involves deferring the loading of non-essential resources until they are needed. In React, lazy loading is commonly used with React.lazy() and Suspense to load components asynchronously, improving performance.

      What is the significance of shouldComponentUpdate in React?

        shouldComponentUpdate is a lifecycle method that determines if a component should re-render or not. By default, it returns true, but you can implement custom logic to optimize performance by preventing unnecessary re-renders.

        What is the purpose of React Fragments?

          React Fragments provide a way to group multiple children elements without adding extra nodes to the DOM. They improve code readability and maintainability by avoiding unnecessary wrapper elements.

          How do you optimize performance in React applications?

            Performance optimization in React involves techniques like code-splitting, memoization, lazy loading, minimizing re-renders with PureComponent or React.memo, and using tools like React Profiler and Chrome DevTools for profiling.

            Explain the concept of PureComponent in React.

              PureComponent is a class component in React that automatically implements shouldComponentUpdate with a shallow prop and state comparison. It helps to prevent unnecessary re-renders by optimizing component performance.

              What are controlled components in React?

                Controlled components are form elements whose value is controlled by React state. Changes to the input value are handled by React, making it easy to manipulate and validate form data.

                What are React hooks rules?

                  React hooks have a few rules: they should only be called at the top level of a functional component or custom hook, they should not be called conditionally, and they should always be called from React functions (not regular JavaScript functions).

                  How do you perform server-side rendering (SSR) with React?

                    Server-side rendering in React involves rendering React components on the server and sending the generated HTML to the client. Libraries like Next.js or custom server setups with ReactDOMServer can be used to implement SSR.

                    Explain the concept of memoization in React.

                      Memoization is a technique used to optimize performance by caching the results of expensive function calls and returning the cached result when the same inputs occur again. React provides useMemo and useCallback hooks for memoization.

                      What is React Router and how does it work?

                        React Router is a popular library for routing in React applications. It allows defining dynamic routes, handling navigation, and rendering different components based on the URL. React Router works by synchronizing the URL with the UI using the history API.

                        How do you handle errors in React?

                        Error handling in React can be done using Error Boundaries, which are special components that catch JavaScript errors in their child component tree. They provide a way to gracefully handle errors and display fallback UI.

                        These are some advanced ReactJS interview questions along with their answers. Understanding these concepts can help you excel in React interviews and build efficient React applications.


                        To summarise, mastering advanced ReactJS concepts requires dedication, practice, and a deep understanding of its principles. Consider honing your skills with the help of a React JS Course. Additionally, stay updated with industry trends, and build real-world projects. With this, you’ll be well-equipped to excel in advanced React interviews and contribute effectively to React-based projects.