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I'm new to JavaScript so forgive me for being a n00b.

When there's intensive calculation required, it more than likely involves loops that are recursive or otherwise. Sometimes this may mean having am recursive loop that runs four functions and maybe each of those functions walks the entire DOM tree, read positions and do some math for collision detection or whatever.

While the first function is walking the DOM tree, the next one will have to wait its for the first one to finish, and so forth. Instead of doing this, why not launch those loops-within-loops separately, outside the programs, and act on their calculations in another loop that runs slower because it isn't doing those calculations itself?

Retarded or clever?

Thanks in advance!

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  • FIRST, why are you walking the dom tree? Why not gather all the DOM elements that could be collided with and put them in an array. I am sure that its only a few that are collision points, not all of them. Second, you can Pseudo multi-thread in javascript using the setTimeout function, e.g. setTimeout(function () {...}, 1); will execute the given function in 1 ms. Commented Feb 5, 2011 at 15:15
  • While not related to your question, you might find looking into Chromes NaCl useful Commented Oct 26, 2012 at 19:46

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Long-term computations are exactly what Web Workers are for. What you describe is the common pattern of producer and/or consumer threads. While you could do this using Web Workers, the synchronization overhead would likely trump any gains even on highly parallel systems.

JavaScript is not the ideal language for computationally demanding applications. Also, processing power of web browser machines can vary wildly (think a low-end smartphone vs. a 16core workstation). Therefore, consider calculating complex stuff on the server and sending the result to the client to display.

For your everyday web application, you should take a single-threaded approach and analyze performance once it becomes a problem. Heck, why not ask for help about your performance problem here?

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JavaScript was never meant to do perform such computationally intensive tasks, and even though this is changing, the fact remains that JavaScript is inherently single-threaded. The recent web workers technology provides a limited form of multi-threading but these worker threads can't access the DOM directly; they can only send/receive messages to the main thread which can then access it on their behalf.

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Currently, the only way to have real parallel processing in JS is to use Web Workers, but it is only supported by very recent browsers. And if your program requires such a thing, it could mean that you are not using the right tools (for example, walking the DOM tree is generally done by using DOM selectors like querySelectorAll).

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