> ## Documentation Index
> Fetch the complete documentation index at: https://docs.stringboot.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Advanced Usage

> Language switching, Performance, and A/B Testing

This guide covers advanced topics for getting the most out of the Stringboot Web SDK.

## Language Switching

Stringboot makes it easy to switch languages dynamically without reloading the page.

### Vanilla JS

```javascript theme={null}
// Switch language
await StringBoot.changeLanguage('es');
// All watched strings and cache are automatically updated!
```

### React

```tsx theme={null}
const [lang, setLang] = useLanguage();
setLang('es'); // Automatically triggers re-render of all useString hooks
```

### Getting Available Languages

You can fetch the list of active languages configured in your dashboard.

```javascript theme={null}
const languages = await StringBoot.getActiveLanguages();

languages.forEach(lang => {
  console.log(`${lang.code}: ${lang.name} (Default: ${lang.isDefault})`);
});
```

### Multi-Tab Synchronization

The SDK automatically synchronizes language changes across browser tabs using the BroadcastChannel API. If a user changes the language in one tab, all other open tabs for your application will instantly update to match.

```javascript theme={null}
// Tab 1: Change language
await StringBoot.changeLanguage('es');

// Tab 2: Automatically receives update!
// All watched strings update across all tabs
```

## Performance Optimization

Stringboot is designed for high performance with minimal impact on your application's load time.

### Caching Strategy

1. **Memory Cache**: Sub-millisecond access for frequently used strings.
2. **IndexedDB**: Persistent offline storage. Strings are loaded from here on startup.
3. **Network**: Only used for initial fetch or delta updates.

### Monitoring Cache Stats

You can inspect the cache usage to debug performance issues.

```javascript theme={null}
// Get cache statistics
const stats = await StringBoot.getCacheStats();

console.log('Memory cache:', stats.memory);
console.log('Database stats:', stats.db);
```

### Parallel Loading

When fetching strings dynamically (outside of hooks), use `Promise.all` to fetch them in parallel.

```javascript theme={null}
// ❌ Sequential (Slower)
const name = await StringBoot.get('name');
const desc = await StringBoot.get('desc');

// ✅ Parallel (Faster)
const [name, desc] = await Promise.all([
  StringBoot.get('name'),
  StringBoot.get('desc')
]);
```

## A/B Testing Integration

Stringboot supports native A/B testing for string variations. You can pass an `analyticsHandler` during initialization to track experiment exposure.

```javascript theme={null}
await StringBoot.initialize({
  apiToken: 'YOUR_API_TOKEN',
  analyticsHandler: (experiment) => {
    // Integrate with your analytics provider (Google Analytics, Mixpanel, etc.)
    console.log('User exposed to experiment:', experiment);
    
    // Example: Mixpanel
    // mixpanel.track('Experiment Viewed', experiment);
  }
});
```

When a user requests a string that is part of an experiment, Stringboot will:

1. Deterministically assign a variant (Control or Variant B) based on the user's session.
2. Return the appropriate string value.
3. Trigger the `analyticsHandler` callback so you can log the exposure.