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Use localStorage to store key-value pairs without expiration time, suitable for persistent user preferences, limited to 5–10 MB per domain name; 2. Use sessionStorage to store session-level data, close the tab page and clear it, suitable for temporary form data; 3. Use IndexedDB to store a large amount of structured data, support transactions and asynchronous operations, suitable for offline priority applications; 4. Use Cache API to cache network resources with Service Worker to achieve offline access to static resources, suitable for PWA; 5. Web SQL has been deprecated and new projects are not recommended; use Cache API to cache static resources, IndexedDB or localStorage to store dynamic data, which can achieve complete offline functions, and the appropriate solution should be selected according to needs.
You can store data offline in HTML5 using several client-side storage options that allow web applications to work without an internet connection. Here are the main methods:
1. Local Storage
localStorage lets you store key-value pairs in the browser with no expiration time. The data remains even after the browser is closed.
Example:
// Save data localStorage.setItem('username', 'john_doe'); // Retrieve data let username = localStorage.getItem('username'); // Remove data localStorage.removeItem('username');
- Use case: User preferences, settings, or cached content that persists across sessions.
- Limit: Typically around 5–10 MB per domain.
2. Session Storage
sessionStorage is similar to localStorage , but data is cleared when the page session ends (ie, when the tab or browser is closed).
Example:
sessionStorage.setItem('tempData', 'temporary value');
- Use case: Data that only needs to last during a single browser session, like form inputs or tab-specific state.
3. IndexedDB
A more powerful option for storing large amounts of structured data, including files and blobs. It's a low-level API for client-side storage of significant amounts of data.
Key features:
- Supports transactions
- Can store complex objects
- Asynchronous API (doesn't block the main thread)
Example usage:
let request = indexedDB.open('MyDatabase', 1);
request.onsuccess = function(event) {
let db = event.target.result;
let transaction = db.transaction(['users'], 'readwrite');
let store = transaction.objectStore('users');
store.add({name: 'John', email: 'john@example.com'});
};- Use case: Offline-first apps, storing large datasets, or caching application data.
4. Cache API (with Service Workers)
The Cache API allows you to store network requests and responses, enabling offline access to assets like HTML, CSS, JS, and images.
Typical use with a service worker:
self.addEventListener('install', event => {
event.waitUntil(
caches.open('v1').then(cache => {
return cache.addAll([
'/',
'/styles.css',
'/app.js'
]);
})
);
});- Use case: Progressive Web Apps (PWAs) that need to load offline or in poor network conditions.
5. Web SQL (Deprecated)
Although not part of the official HTML5 standard and deprecated, some browsers still support Web SQL for SQL-based storage. However, it's not recommended for new projects.
To enable full offline functionality, combine service workers with Cache API and IndexedDB :
- Cache static assets via the Cache API
- Store dynamic data using IndexedDB or localStorage
This way, your app can load and function even when the user is offline.
Basically, choose the right tool based on your needs: simple key-value use localStorage , complex or large data use IndexedDB , and static assets use Cache API .
The above is the detailed content of How can you store data offline using HTML5?. For more information, please follow other related articles on the PHP Chinese website!
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