Web Workers
Multithreaded Programs in JavaScript
Publisher: O'Reilly Media
Final Release Date: May 2012
Pages: 62

Web apps would run much better if heavy calculations could be performed in the background, rather than compete with the user interface. With this book, you’ll learn how to use Web Workers to run computationally intensive JavaScript code in a thread parallel to the UI. Yes, multi-threaded programing is complicated, but Web Workers provide a simple API that helps you be productive without the complex algorithms.

If you have an intermediate to advanced understanding of JavaScript—especially event handling and callbacks—you’re ready to tackle Web Workers with the tools in this example-driven guide.

  • Start creating Web Workers and understand what they can and can’t do
  • Determine which browser versions support the API
  • Use dedicated Web Workers for tasks that consume a lot of CPU, such as data parsing
  • Explore use cases for creating inline Workers, such as encapsulating a web app in one page
  • Create a shared Worker to communicate multiple web app instances to the server, and other uses
  • Learn best practices for debugging Web Workers
  • Apply Web Workers within the server-side Node environment
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(1 of 1 customers found this review helpful)


O'Reilly Web Workers: Multithreaded JS

By Lewis Cowles

from Essex, UK

About Me Developer, Educator

Verified Reviewer


  • Accurate
  • Concise
  • Easy to understand
  • Helpful examples


  • Too basic

Best Uses

  • Expert
  • Intermediate
  • Novice
  • Student

Comments about oreilly Web Workers:

I recently read a book by an up and coming new Author, Ido Green. His book Web Workers, Multithreaded Programs in JavaScript (O'Reilly, 2012) is about the shiny new technology called web-workers. Basically it allows for multi-threaded JavaScript in the browser, to apparently take the load off of the page and allow a more seamless, jerk-free experience. The book is quite a short book–at, it could easily be mistaken for a chapter from another technical book, but it's actually just more concise than other books. I found it refreshing that Ido decided to cut the fluff and get right into the nitty-gritty of what at first seems to be a very exciting technology, for web developers at least.

Another reason that the book is quite short is that it covers a pretty basic topic, but I would feel more comfortable keeping my copy as a technical reference. There are a few caveats, as with any free and open technology, it seems that data intensive threads or working on inter-thread tasks may be a bit tricky if not downright impossible, and the book does seem to take this fact lying down, but I suppose it's better than trying a neat hack that will be patched in newer browser versions.

One thing that really struck me with the book was the encyclopedic format, with Author Green, typically providing concise explanations, followed by demonstrations of the features in action, with relevant code examples. This did remind me of a blogging or online tutorial pro-forma. Also following the wonder that is GitHub, Sample code has it's very own Github repo, as mentioned in the final chapter and don't expect to touch the DOM with this web-worker magic.

In short Web-workers is a very good read, and I would say that for the developer that doesn't have much time, that wants to brush-up on their skills or learn about an entirely new topic web-workers is a really good way to bring yourself up to speed. My only concern is the immaturity of the technology, and if that were legitimate we'd all be running around in msdos. If you need more info I thoroughly recommend the book, you wont be disappointed.

For more information on this book

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Get the book directly from O'Reilly.

Note that there is also a kindle version available, if that lights your fire (no pun intended… okay maybe that's a lie)

Disclosure: This book was received as a part of the O'Reilly Blogger Review Programme

(4 of 5 customers found this review helpful)


Important Concepts, poor examples

By Piemaster

from Waterloo, ON

About Me Developer, Sys Admin

Verified Reviewer



    • Confusing Examples
    • Not comprehensive enough

    Best Uses

      Comments about oreilly Web Workers:

      I am a member of a O'Reilly user group and we were sent this book in order to have it reviewed by the community. My profession is that of a web programmer that I have been doing for 17 years, with lots of JavaScript experience.

      "Web Workers" covers some important material with regards to the HTML 5 Worker API and its effective use.

      But, if you want to learn about concepts related to this topic I would suggest finding another book. This one has very long examples that due to that length lose the point that is trying to be shown.

      There is no treatment for how to make use of this in the real browser space. I think that coverage of how to gracefully (or awkwardly even) ensure that your processes will run when Worker is not available.

      While covering this sort of material it would also be a good time to mention best use of setImmediate and requestAnimationFrame which are related concepts.

      To sum up, this book should have been much, much, shorter - effectively a Web Worker cheat sheet - or it should have been longer with a more robust treatment of intense processing techniques in JavaScript.

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