Lesson overview · Free interview practice

Web Workers

Master multithreading with Web Workers.

Topics in the full lesson
  • Introduction to Web Workers
  • Creating and Using Web Workers
  • Communication with Web Workers
  • Types of Web Workers
  • Data Transfer Between Threads
  • Error Handling in Web Workers
  • Best Practices
  • Exercises

Practice Problems

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TheoryEasy

Communicating with Workers via `postMessage`

Question

How does the main thread communicate with a Web Worker? Show the full bidirectional pattern and the structured-cloning constraint.

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

Worker Types: Dedicated / Shared / Inline

Question

What are the three types of Web Workers, and when do you reach for each?

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Explain your reasoning or try an implementation before comparing answers.

TheoryEasy

What is a Web Worker

Question

What is a Web Worker, and what are its constraints? Show the canonical main-thread + worker setup.

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Worker Error Handling + Termination

Question

How do errors propagate from a Web Worker to the main thread? When do you use worker.terminate() vs self.close()?

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Explain your reasoning or try an implementation before comparing answers.

TheoryMedium

Structured Cloning vs Transferable Objects

Question

For large data, postMessage's structured-cloning algorithm has a meaningful cost. What are transferable objects, and how do they change the postMessage semantics?

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Explain your reasoning or try an implementation before comparing answers.

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