HTML Web Workers

⚙️ HTML Web Workers

HTML Web Workers let you run JavaScript in the background thread, separate from the main UI thread. This allows heavy processing without freezing or slowing down the web page.

They’re useful when:

• Performing CPU-intensive tasks
• Parsing large data
• Running real-time computations

🧠 What is a Web Worker?

A Web Worker is a separate JavaScript file that runs in parallel to your main JS code:

• No access to DOM or window
• Communicates via postMessage() and onmessage
• Doesn’t block UI or input events

🚀 When to Use Web Workers

Use Web Workers when you need to:

• Do large calculations
• Fetch and process big data sets
• Offload heavy logic from the main thread
• Improve app responsiveness

🛠️ How to Use Web Workers

🔹 Step 1: Create the Worker File

🔹 Step 2: Use It in HTML

🔄 Communication Flow

• Main → Worker: worker.postMessage(data)
• Worker → Main: postMessage(result) and worker.onmessage

🚫 Limitations of Web Workers

• ❌ Cannot access the DOM
• ❌ Cannot use window, document, alert(), etc.
• ✅ Can use AJAX, timers, and import scripts

🔁 Types of Web Workers

🧠 Key Takeaways

• Web Workers allow you to run JS code off the main thread
• Ideal for long-running or computationally heavy operations
• Communicate using postMessage()/onmessage
• Cannot access the DOM or browser-specific APIs
• Improves UI responsiveness in complex apps