React.JS Mock Interview | Interview Questions for Senior React.JS Developers

Summary

In this mock interview, React.js developer Rakib shares insights on key React concepts with interviewer Jose. They discuss differences between class-based and functional components, the virtual DOM, and state management tools like Redux. Rakib highlights his experience with React hooks, testing with Jest, and deployment strategies using Docker and Nginx. The conversation emphasizes best practices for coding, debugging, and performance optimization in React applications. Rakib offers practical advice for learners, underscoring the importance of getting hands-on with React to build skills. This interview is a valuable resource for developers looking to strengthen their React knowledge.

Takeaways

• 😀 React allows building components with JavaScript logic to create dynamic UIs.
• 😀 Functional components are preferred over class components due to simplicity and the introduction of hooks.
• 😀 The virtual DOM improves performance by updating only the necessary parts of the UI, rather than re-rendering the entire DOM.
• 😀 Redux is a state management library that centralizes the application state, making it easier to manage and debug.
• 😀 Testing React apps is essential to ensure data flows correctly and to catch potential issues in the UI.
• 😀 Tools like Jest and React Testing Library are widely used for testing React components and apps.
• 😀 Docker is a helpful tool for packaging and deploying applications in a consistent environment across different systems.
• 😀 Code splitting is a performance optimization technique where large JavaScript files are broken into smaller chunks to load only the necessary code.
• 😀 Best practices in React development include modularizing components, following the single responsibility principle, and using consistent code formatting.
• 😀 Hands-on coding is the best way to learn React. The official React documentation and project-based learning are recommended for beginners.

Q & A

What is the main focus of Jose as a technical recruiter?

Jose's main focus as a technical recruiter is to hire the best engineers and assist them in the vetting process. He has over 17 years of experience in the software industry, specializing in JavaScript.

What has been Rakib's career path and his shift in technology focus?

Rakib has been programming for around eight years. He started with Java but transitioned to JavaScript in recent years, particularly enjoying work with JavaScript-based technologies such as React.

What project is Rakib currently working on, and what technologies is he using?

Rakib is working on a finance application for a company called Meltwater. The front-end is built using React.js, and he consumes APIs to display stock market and cryptocurrency data in a format needed by their analysts.

What is the difference between React class components and functional components?

Class components are the older version of React components, using lifecycle methods and state management within the class itself. Functional components, introduced later, use hooks for managing state and side effects, offering a simpler and more modular approach.

When would you choose class components over functional components in React?

Class components may be preferred when there is complex state logic, when more granular control over lifecycle methods is required, or when integrating features like Redux, which may not have full support in functional components.

Can you explain the concept of the Virtual DOM in React?

The Virtual DOM is an in-memory representation of the real DOM. React uses it to optimize UI rendering by comparing changes in the Virtual DOM and only updating the real DOM with the necessary changes, improving performance.

How does React's Virtual DOM differ from traditional DOM manipulation?

In traditional DOM manipulation (e.g., with jQuery), developers directly modify the DOM elements. In React, the Virtual DOM handles updates and synchronization with the real DOM, allowing React to manage the UI more efficiently and selectively.

What tools or libraries can be used for global state management in React applications?

One of the most popular tools for global state management in React is Redux. It allows the central management of application state in a single object, where actions and reducers are used to update the state and trigger UI changes.

How does Redux work in React applications?

Redux maintains a global state tree, where the entire application's state is stored. When something in the state changes, an action is dispatched, and reducers handle updating the state. React components can then subscribe to the store and re-render based on state changes.

What are some best practices in React development that Rakib follows?

Rakib follows the Single Responsibility Principle for components, emphasizing that components should handle only one responsibility. He also advocates for modularizing components, using a linter for consistent code formatting, and preferring functional components where appropriate.

What is code splitting in React, and why is it important?

Code splitting is the practice of dividing large JavaScript files into smaller chunks to load only the necessary code for a given screen or feature. This improves performance by reducing the initial load time and helps in creating scalable React applications.

How does React optimize state updates when multiple setState calls are made?

React batches state updates to optimize performance. If multiple setState calls are made in a single event handler, React groups them together and triggers only one re-render, rather than re-rendering after each individual state change.

How does Rakib deploy a React application, and what is his experience with Docker?

Rakib typically deploys React applications by building them and serving them with NGINX. He also has experience using Docker to containerize applications, which helps avoid issues with restrictive security policies on development machines.

What advice does Rakib give to developers learning React?

Rakib advises developers to start coding React as soon as possible rather than just reading tutorials. He recommends referring to the official React documentation, which is an excellent resource for both beginners and experienced developers.