Networking

The react-native-webworker library includes built-in networking support for your worker threads. Every worker automatically gets the familiar browser fetch() API.

How it works

Every worker comes with a complete Fetch API implementation built-in. Behind the scenes, it uses the platform’s native networking:

• iOS: Uses NSURLSession for HTTP requests
• Android: Uses OkHttp for HTTP requests

This ensures good performance and handles platform-specific requirements like SSL certificates, proxy settings, and connection reuse.

Fetch API

Workers include a basic Fetch API for making HTTP requests. It is a simplified version compared to the full browser implementation.

Basic usage

Here is how to make requests:

// Simple GET request
const response = await fetch('https://jsonplaceholder.typicode.com/todos/1');
const data = await response.json();
console.log(data);

// POST request with JSON data
const response = await fetch('https://jsonplaceholder.typicode.com/posts', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({
    title: 'foo',
    body: 'bar',
    userId: 1
  })
});

if (response.ok) {
  const result = await response.json();
  console.log(result);
}

Supported options

Currently, these fetch options work:

const response = await fetch('https://api.example.com/data', {
  method: 'POST', // HTTP method like 'GET', 'POST', 'PUT', 'DELETE'
  headers: {
    'Authorization': 'Bearer token123',
    'Content-Type': 'application/json'
  },
  body: JSON.stringify({ key: 'value' }), // String or ArrayBuffer
  timeout: 5000, // Request timeout in milliseconds
  redirect: 'follow', // 'follow', 'error', or 'manual' (Android only currently)
  mode: 'cors' // Accepted but ignored (Native requests are not subject to CORS)
});

Note

Advanced options like credentials and signal are not supported yet.

Response format

The fetch() function returns a basic response object with these properties:

const response = await fetch('https://api.example.com/data');

// Basic response info
console.log(response.status); // 200
console.log(response.ok); // true (quick way to check if status is 200-299)

// Get response headers (as a plain object)
console.log(response.headers['content-type']); // 'application/json'

// Read the response body
const text = await response.text(); // Get as plain text
const json = await response.json(); // Parse as JSON
const arrayBuffer = await response.arrayBuffer(); // Get as ArrayBuffer

Error handling

Fetch provides basic error handling:

try {
  const response = await fetch('https://api.example.com/data');

  if (!response.ok) {
    // Check for HTTP errors (like 404, 500, etc.)
    throw new Error(`HTTP ${response.status}: ${response.statusText}`);
  }

  const data = await response.json();
  console.log(data);

} catch (error) {
  // Network errors (DNS failure, connection issues, etc.)
  console.error('Request failed:', error.message);
}

Request body types

You can send different types of data in your requests:

Text and JSON

// Plain text
await fetch('/api', {
  method: 'POST',
  body: 'Hello World'
});

// JSON objects (automatically converted to strings)
await fetch('/api', {
  method: 'POST',
  body: { message: 'Hello' } // Gets turned into '{"message":"Hello"}'
});

Binary data

// ArrayBuffer
const buffer = new ArrayBuffer(1024);
await fetch('/api/upload', {
  method: 'POST',
  body: buffer
});

// Typed arrays
const uint8Array = new Uint8Array([1, 2, 3, 4]);
await fetch('/api/upload', {
  method: 'POST',
  body: uint8Array
});

Current limitations

1. Limited Fetch Options: Advanced options like credentials and signal aren’t supported yet.
2. No XMLHttpRequest: The XMLHttpRequest API isn’t implemented.
3. No AbortController: Request cancellation isn’t available yet.
4. No Request/Response Classes: You can’t create new Request() or new Response() objects - just use the basic fetch() function.
5. No Headers Class: Headers are plain JavaScript objects, not Header class instances.
6. No FormData: Multipart form data isn’t supported - use JSON or URL-encoded strings instead.
7. No WebSocket Support: Only HTTP requests work, no WebSocket connections.