Offline Functionality for Installable Apps

1. Introduction

Progressive Web Apps (PWAs) provide a native app-like experience for users, including offline functionality. This lesson covers how to implement offline capability in installable PWAs, enhancing user experience by allowing access to content without an internet connection.

2. Key Concepts

• **Progressive Web Apps**: Web applications that use modern web capabilities to deliver an app-like experience.
• **Offline Functionality**: The ability for an app to function without an internet connection.
• **Service Workers**: Background scripts that intercept network requests, enabling caching and offline capabilities.

3. Service Workers

Service Workers are JavaScript files that run separately from the main browser thread, allowing you to manage caching and intercept requests. They are a crucial component for enabling offline functionality.

if ('serviceWorker' in navigator) {
    window.addEventListener('load', () => {
        navigator.serviceWorker.register('/service-worker.js')
            .then(registration => {
                console.log('Service Worker registered with scope:', registration.scope);
            })
            .catch(error => {
                console.error('Service Worker registration failed:', error);
            });
    });
}
            

4. Caching Strategies

Implementing caching strategies is vital for offline functionality. The following are common caching strategies:

1. Cache First: Check the cache first, and if the resource is not available, fetch from the network.
2. Network First: Try fetching from the network first, and fallback to the cache if the network request fails.
3. Cache with Network Fallback: Use the cache for immediate response, while updating the cache with the latest version from the network.

4.1 Example: Cache First Strategy

self.addEventListener('install', event => {
    event.waitUntil(
        caches.open('v1').then(cache => {
            return cache.addAll([
                '/',
                '/index.html',
                '/styles.css',
                '/script.js'
            ]);
        })
    );
});

self.addEventListener('fetch', event => {
    event.respondWith(
        caches.match(event.request).then(response => {
            return response || fetch(event.request);
        })
    );
});
        

5. Best Practices

6. FAQ