Web Workers

// worker.js (Worker file)
self.onmessage = function(e) {
  const name = e.data;
  self.postMessage('Hello, ' + name + '!');
};

// main.js (Main thread)
const worker = new Worker('worker.js');

// Send message to worker
worker.postMessage('Alice');

// Receive message from worker
worker.onmessage = function(e) {
  console.log(e.data); // "Hello, Alice!"
};

// Terminate worker when done
worker.terminate();

// fibonacci-worker.js
self.onmessage = function(e) {
  const n = e.data;
  
  function fibonacci(num) {
    if (num <= 1) return num;
    return fibonacci(num - 1) + fibonacci(num - 2);
  }
  
  const result = fibonacci(n);
  self.postMessage(result);
};

// main.js
const worker = new Worker('fibonacci-worker.js');

worker.postMessage(40);

worker.onmessage = function(e) {
  console.log('Fibonacci result:', e.data);
  worker.terminate();
};

worker.onerror = function(error) {
  console.error('Worker error:', error.message);
};

// filter-worker.js
self.onmessage = function(e) {
  const { data, minPrice, maxPrice } = e.data;
  
  // Filter products by price range
  const filtered = data.filter(product => {
    return product.price >= minPrice && product.price <= maxPrice;
  });
  
  // Sort by price
  filtered.sort((a, b) => a.price - b.price);
  
  self.postMessage(filtered);
};

// main.js
const worker = new Worker('filter-worker.js');

const products = [
  { name: 'Product 1', price: 100 },
  { name: 'Product 2', price: 200 },
  { name: 'Product 3', price: 50 },
  // ... thousands more products
];

worker.postMessage({
  data: products,
  minPrice: 50,
  maxPrice: 150
});

worker.onmessage = function(e) {
  console.log('Filtered products:', e.data);
  displayProducts(e.data);
  worker.terminate();
};

// safe-worker.js
self.onmessage = function(e) {
  try {
    const result = performCalculation(e.data);
    self.postMessage({ success: true, result });
  } catch (error) {
    self.postMessage({ 
      success: false, 
      error: error.message 
    });
  }
};

// main.js
const worker = new Worker('safe-worker.js');

worker.postMessage(data);

worker.onmessage = function(e) {
  if (e.data.success) {
    console.log('Success:', e.data.result);
  } else {
    console.error('Worker error:', e.data.error);
  }
};

worker.onerror = function(error) {
  console.error('Worker crashed:', error.message);
  console.error('Line:', error.lineno);
  console.error('File:', error.filename);
};