// Before: Inefficient array operations
const sorted = users.slice().sort((a, b) => a.age - b.age);
const modified = sorted.map(user => ({ ...user, active: true }));

// After: Modern immutable methods
const sorted = users.toSorted((a, b) => a.age - b.age);
const modified = sorted.with(user => ({ ...user, active: true }));

// Advanced concurrency with error handling
async function fetchWithFallback(urls) {
  const results = await Promise.allSettled(
    urls.map(url => fetch(url).then(r => r.json()))
  );
  
  return results
    .filter(result => result.status === 'fulfilled')
    .map(result => result.value);
}

// WeakMap for private data without memory leaks
const privateData = new WeakMap();
class Resource {
  constructor(data) {
    privateData.set(this, { processed: false, cache: new Map() });
  }
}

// Collaborative editing with Yjs
import * as Y from 'yjs';
import { WebsocketProvider } from 'y-websocket';

const doc = new Y.Doc();
const provider = new WebsocketProvider(
  'wss://collab.example.com',
  'document-id',
  doc
);

const text = doc.getText('content');
text.observe(event => {
  // Handle remote changes
});

// Dependency injection container
const container = createContainer();

container.register('UserService', UserService);
container.register('OrderService', OrderService);

// Middleware composition
const app = express();
app.use(correlationId());
app.use(requestLogging());
app.use(authentication());
app.use(container.middleware());

// Graceful shutdown
process.on('SIGTERM', async () => {
  await container.dispose();
  server.close();
});