Question 67

Question

Explain the difference between Worker and SharedWorker in web workers.

Answer

1. Worker:

• Purpose: Designed for individual tasks that need to run independently.

• Isolation: Each Worker instance operates completely isolated from other workers and the main thread. They have their own separate scopes, variables, and memory.

• Communication: Communication with a Worker is done using messages:

  • The main thread sends messages to the worker using worker.postMessage().

  • The worker responds to the main thread by sending messages back through onmessage events on the main thread.

2. SharedWorker:

• Purpose: Primarily for scenarios where multiple scripts (or different parts of the same script) need to share data and communicate in a synchronized way.

• Sharing: Multiple tabs or windows can connect to the same SharedWorker instance, allowing them to share data and collaborate on tasks.

• Communication:

  • Similar message-based communication as Worker, using postMessage() and onmessage.

  • The SharedWorker maintains a global state accessible by all connected clients. Changes made by one client are immediately visible to others.

When to Use Which:

Feature	Worker	SharedWorker
Isolation	High - Each worker is completely separate	Lower - Multiple scripts share state
Communication	Message-based, one-to-one with main thread	Message-based, multiple clients share state
Use Cases	Intensive computations, background tasks	Data sharing between tabs/windows, collaborative applications

In a nutshell: Worker is for isolated tasks that don't need to share data. SharedWorker is for scenarios where collaboration and shared data are essential.