What are Web Workers in JavaScript?

Web Workers allow running JavaScript in background threads, separate from the main UI thread.

Creating a Web Worker:

worker.js:

// Heavy computation
self.onmessage = function(e) {
  const { numbers } = e.data;
  const result = numbers.reduce((sum, num) => sum + num, 0);
  
  // Send result back
  self.postMessage({ result });
};

main.js:

const worker = new Worker("worker.js");
// Send data to worker
worker.postMessage({ numbers: [1, 2, 3, 4, 5] });
// Receive result
worker.onmessage = function(e) {
  console.log("Result:", e.data.result);
};
// Handle errors
worker.onerror = function(error) {
  console.error("Worker error:", error);
};
// Terminate worker
worker.terminate();

Types of Workers:
1. Dedicated Workers - single script
2. Shared Workers - multiple scripts
3. Service Workers - network proxy

Benefits:
- Non-blocking operations
- CPU-intensive tasks
- Parallel processing
- Better user experience

Limitations:
- No DOM access
- Limited API access
- Communication overhead