Workers

Basic Worker

// src/index.ts
export default {
  async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
    const url = new URL(request.url);
    
    if (url.pathname === '/api/hello') {
      return Response.json({ message: 'Hello from the edge!' });
    }
    
    return new Response('Not Found', { status: 404 });
  },
};

wrangler.toml Configuration

name = "my-worker"
main = "src/index.ts"
compatibility_date = "2024-01-01"

[vars]
ENVIRONMENT = "production"

# KV Namespace
[[kv_namespaces]]
binding = "MY_KV"
id = "abc123"

# D1 Database
[[d1_databases]]
binding = "DB"
database_name = "my-database"
database_id = "def456"

# R2 Bucket
[[r2_buckets]]
binding = "BUCKET"
bucket_name = "my-bucket"

# AI
[ai]
binding = "AI"

# Durable Objects
[[durable_objects.bindings]]
name = "COUNTER"
class_name = "Counter"

[[migrations]]
tag = "v1"
new_classes = ["Counter"]

Request Routing

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    const { pathname } = url;
    
    // Router pattern
    const routes: Record<string, () => Promise<Response>> = {
      '/api/users': () => handleUsers(request, env),
      '/api/posts': () => handlePosts(request, env),
    };
    
    const handler = routes[pathname];
    if (handler) {
      return handler();
    }
    
    // Wildcard matching
    if (pathname.startsWith('/api/users/')) {
      const userId = pathname.split('/')[3];
      return handleUser(userId, request, env);
    }
    
    return new Response('Not Found', { status: 404 });
  },
};

KV Storage

interface Env {
  MY_KV: KVNamespace;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    
    // Set value
    await env.MY_KV.put('key', 'value', {
      expirationTtl: 3600, // 1 hour
      metadata: { created: Date.now() },
    });
    
    // Get value
    const value = await env.MY_KV.get('key');
    
    // Get with metadata
    const { value: data, metadata } = await env.MY_KV.getWithMetadata('key');
    
    // List keys
    const list = await env.MY_KV.list({ prefix: 'user:' });
    
    // Delete
    await env.MY_KV.delete('key');
    
    return Response.json({ value });
  },
};

D1 Database (SQLite)

interface Env {
  DB: D1Database;
}

// Create tables (run once via wrangler d1 execute)
// wrangler d1 execute my-database --file=./schema.sql

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Query
    const { results } = await env.DB.prepare(
      'SELECT * FROM users WHERE id = ?'
    ).bind(1).all();
    
    // Insert
    const { meta } = await env.DB.prepare(
      'INSERT INTO users (name, email) VALUES (?, ?)'
    ).bind('Alice', 'alice@example.com').run();
    
    // Batch operations
    const batch = await env.DB.batch([
      env.DB.prepare('INSERT INTO logs (action) VALUES (?)').bind('login'),
      env.DB.prepare('UPDATE users SET last_login = ? WHERE id = ?').bind(Date.now(), 1),
    ]);
    
    // First result only
    const user = await env.DB.prepare(
      'SELECT * FROM users WHERE email = ?'
    ).bind('alice@example.com').first();
    
    return Response.json({ results, insertId: meta.last_row_id });
  },
};

Schema Example

-- schema.sql
CREATE TABLE IF NOT EXISTS users (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  name TEXT NOT NULL,
  email TEXT UNIQUE NOT NULL,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP
);

CREATE TABLE IF NOT EXISTS posts (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  user_id INTEGER NOT NULL,
  title TEXT NOT NULL,
  content TEXT,
  FOREIGN KEY (user_id) REFERENCES users(id)
);

R2 Object Storage

interface Env {
  BUCKET: R2Bucket;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const url = new URL(request.url);
    const key = url.pathname.slice(1);
    
    switch (request.method) {
      case 'PUT': {
        // Upload file
        const body = await request.arrayBuffer();
        await env.BUCKET.put(key, body, {
          httpMetadata: {
            contentType: request.headers.get('content-type') || 'application/octet-stream',
          },
          customMetadata: {
            uploadedBy: 'api',
          },
        });
        return new Response('Uploaded', { status: 201 });
      }
      
      case 'GET': {
        // Download file
        const object = await env.BUCKET.get(key);
        if (!object) {
          return new Response('Not Found', { status: 404 });
        }
        
        const headers = new Headers();
        object.writeHttpMetadata(headers);
        headers.set('etag', object.httpEtag);
        
        return new Response(object.body, { headers });
      }
      
      case 'DELETE': {
        await env.BUCKET.delete(key);
        return new Response('Deleted');
      }
      
      default:
        return new Response('Method Not Allowed', { status: 405 });
    }
  },
};

// List objects
async function listObjects(env: Env, prefix?: string) {
  const listed = await env.BUCKET.list({
    prefix,
    limit: 100,
  });
  return listed.objects.map(obj => ({
    key: obj.key,
    size: obj.size,
    uploaded: obj.uploaded,
  }));
}

Cloudflare AI

interface Env {
  AI: Ai;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const { prompt } = await request.json();
    
    // Text generation (Llama, Mistral, etc.)
    const response = await env.AI.run('@cf/meta/llama-3-8b-instruct', {
      messages: [
        { role: 'system', content: 'You are a helpful assistant.' },
        { role: 'user', content: prompt },
      ],
      max_tokens: 1024,
    });
    
    return Response.json(response);
  },
};

// Image generation
async function generateImage(env: Env, prompt: string) {
  const response = await env.AI.run('@cf/stabilityai/stable-diffusion-xl-base-1.0', {
    prompt,
    num_steps: 20,
  });
  
  return new Response(response, {
    headers: { 'content-type': 'image/png' },
  });
}

// Text embeddings
async function getEmbeddings(env: Env, text: string) {
  const response = await env.AI.run('@cf/baai/bge-base-en-v1.5', {
    text: [text],
  });
  return response.data[0]; // Float32Array
}

// Image classification
async function classifyImage(env: Env, imageData: ArrayBuffer) {
  const response = await env.AI.run('@cf/microsoft/resnet-50', {
    image: [...new Uint8Array(imageData)],
  });
  return response;
}

// Speech to text
async function transcribe(env: Env, audioData: ArrayBuffer) {
  const response = await env.AI.run('@cf/openai/whisper', {
    audio: [...new Uint8Array(audioData)],
  });
  return response.text;
}

Durable Objects

// Durable Object class
export class Counter {
  state: DurableObjectState;
  
  constructor(state: DurableObjectState) {
    this.state = state;
  }
  
  async fetch(request: Request): Promise<Response> {
    const url = new URL(request.url);
    
    let value = (await this.state.storage.get<number>('count')) || 0;
    
    switch (url.pathname) {
      case '/increment':
        value++;
        await this.state.storage.put('count', value);
        break;
      case '/decrement':
        value--;
        await this.state.storage.put('count', value);
        break;
    }
    
    return Response.json({ count: value });
  }
}

// Worker using Durable Object
interface Env {
  COUNTER: DurableObjectNamespace;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Get unique ID for this counter (e.g., per user)
    const counterId = env.COUNTER.idFromName('global-counter');
    const counter = env.COUNTER.get(counterId);
    
    // Forward request to Durable Object
    return counter.fetch(request);
  },
};

Cloudflare Pages

pages.toml (Functions Config)

[build]
command = "npm run build"
output_directory = "dist"

[[redirects]]
from = "/old-page"
to = "/new-page"
status = 301

[[headers]]
for = "/api/*"
[headers.values]
Access-Control-Allow-Origin = "*"

Pages Functions

// functions/api/hello.ts
export const onRequestGet: PagesFunction = async (context) => {
  return Response.json({ message: 'Hello!' });
};

export const onRequestPost: PagesFunction<Env> = async (context) => {
  const body = await context.request.json();
  
  // Access bindings
  await context.env.KV.put('key', JSON.stringify(body));
  
  return Response.json({ success: true });
};

// functions/api/users/[id].ts
export const onRequestGet: PagesFunction = async (context) => {
  const userId = context.params.id;
  return Response.json({ userId });
};

// Middleware: functions/_middleware.ts
export const onRequest: PagesFunction = async (context) => {
  // Auth check
  const auth = context.request.headers.get('Authorization');
  if (!auth) {
    return new Response('Unauthorized', { status: 401 });
  }
  
  // Continue to next handler
  return context.next();
};

Queues

// Producer
interface Env {
  MY_QUEUE: Queue;
}

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    // Send message to queue
    await env.MY_QUEUE.send({
      type: 'email',
      to: 'user@example.com',
      subject: 'Welcome!',
    });
    
    // Batch send
    await env.MY_QUEUE.sendBatch([
      { body: { task: 'process', id: 1 } },
      { body: { task: 'process', id: 2 } },
    ]);
    
    return Response.json({ queued: true });
  },
};

// Consumer
export default {
  async queue(batch: MessageBatch<any>, env: Env): Promise<void> {
    for (const message of batch.messages) {
      try {
        await processMessage(message.body);
        message.ack();
      } catch (error) {
        message.retry();
      }
    }
  },
};

Cron Triggers

# wrangler.toml
[triggers]
crons = ["0 0 * * *", "*/15 * * * *"]  # Daily at midnight, every 15 min

export default {
  async scheduled(event: ScheduledEvent, env: Env, ctx: ExecutionContext): Promise<void> {
    switch (event.cron) {
      case '0 0 * * *':
        await dailyCleanup(env);
        break;
      case '*/15 * * * *':
        await checkHealthStatus(env);
        break;
    }
  },
};

WebSockets

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const upgradeHeader = request.headers.get('Upgrade');
    
    if (upgradeHeader === 'websocket') {
      const [client, server] = Object.values(new WebSocketPair());
      
      server.accept();
      server.addEventListener('message', (event) => {
        server.send(`Echo: ${event.data}`);
      });
      
      return new Response(null, {
        status: 101,
        webSocket: client,
      });
    }
    
    return new Response('Expected WebSocket', { status: 400 });
  },
};

Resources

Workers Docs: https://developers.cloudflare.com/workers/
D1 Docs: https://developers.cloudflare.com/d1/
R2 Docs: https://developers.cloudflare.com/r2/
Pages Docs: https://developers.cloudflare.com/pages/
AI Docs: https://developers.cloudflare.com/workers-ai/
Wrangler CLI: https://developers.cloudflare.com/workers/wrangler/

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