Progressive Web Apps (PWA) Interview Questions and Answers for experienced

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100 PWA Interview Questions and Answers

  1. What is a Progressive Web App (PWA)?

    • Answer: A PWA is a web application that uses modern web capabilities to deliver an app-like experience to users. It combines the best of web and mobile apps, offering features like offline functionality, push notifications, and installability, all while being accessible through any web browser without requiring a download from an app store.

  2. Explain the core principles of PWAs.

    • Answer: PWAs are built around the principles of reliability, fast performance, and engaging user experience. Reliability ensures they load instantly even on unreliable networks. Fast performance means they respond quickly to user interactions. Engaging provides a fluid, intuitive, and enjoyable experience.

  3. What are the key technologies used in building PWAs?

    • Answer: Key technologies include service workers (for offline capabilities and push notifications), web app manifest (for installability and metadata), and HTTPS (for secure connections).

  4. How do service workers enable offline functionality in PWAs?

    • Answer: Service workers act as proxies between the web app and the browser. They intercept network requests and can cache static assets (HTML, CSS, JavaScript, images). If the network is unavailable, the service worker can serve the cached content, allowing the app to function offline.

  5. Explain the role of the web app manifest in a PWA.

    • Answer: The web app manifest is a JSON file that provides metadata about the PWA, such as its name, icons, display settings, and start URL. This metadata allows the browser to display the app like a native app when added to the home screen.

  6. How do PWAs handle push notifications?

    • Answer: PWAs use the Push API and service workers to send push notifications to users. The service worker listens for push messages from a server and displays them to the user, even if the app isn't currently open.

  7. What are the benefits of using PWAs over native mobile apps?

    • Answer: Benefits include lower development costs (write once, run anywhere), easier updates (no app store approvals needed), wider reach (accessible on any browser), and better SEO.

  8. What are the limitations of PWAs?

    • Answer: Limitations can include limited access to device hardware (compared to native apps), potential compatibility issues across different browsers, and reliance on a stable internet connection (although offline capabilities mitigate this).

  9. Describe the process of installing a PWA.

    • Answer: The user typically sees an "Add to Home Screen" prompt from their browser. After tapping it, the PWA is added to their device's home screen as an app icon, launching in a fullscreen, standalone mode.

  10. How can you test if your PWA is working correctly?

    • Answer: Use Lighthouse (a Chrome DevTools auditing tool) or similar tools to check for PWA best practices and performance. Manually test offline functionality, push notifications, and installability on different devices and browsers.

  11. Explain different caching strategies for PWAs.

    • Answer: Various strategies exist, including cache-first (serving cached content first, then updating), network-first (fetching from the network, caching if successful), cache-only (serving only cached content), and stale-while-revalidate (serving stale content while updating the cache in the background).

  12. Discuss the lifecycle of a service worker.

    • Answer: A service worker goes through installation, activation, and termination stages. During installation, it registers and caches assets. During activation, it takes over control of network requests. It remains active until terminated or updated.

  13. How can you optimize PWA performance?

    • Answer: Optimizations include compressing images, minimizing HTTP requests, using efficient JavaScript frameworks, implementing lazy loading, and optimizing caching strategies.

  14. What are some common challenges encountered while developing PWAs?

    • Answer: Challenges include debugging service workers, managing cache invalidation, ensuring cross-browser compatibility, handling different network conditions, and optimizing for different device form factors.

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