Techniques or Data Structures For Speeding Up Javascript?

This might be a bit vague.

I'm working on an Atari 2600 emulator in javascript (http://jsatari.com/demo/ and https://github.com/docmarionum1/jsAtari) and it just runs incredibly slow. In chrome around 15-20 FPS and in Firefox around 2-3 FPS (on my computer).

I've run through my code optimizing with Chrome's and Firebug's profilers and optimized whatever I could, but I'm FAR from what I need and I don't see much more room for improvement in my algorithms. (Or, at least not without significantly diverging from the original hardware implementation.)

And so far my biggest improvements haven't come from improving the algorithms, but from changing my data structures:

• Switching my large arrays (thousands of elements) to Typed Arrays provided the biggest boost in performance. Firefox would freeze before the switch, and Chrome ran about 10x faster.

• I replaced some smaller arrays with individual variables and switch statements, also providing a significant boost in performance.

So, it seems p开发者_如何学Goretty clear that arrays are incredibly slow.

In general, performance just seems very finicky, with small changes in my code resulting in large changes to the performance (for better or worse.) Or there other oddities that could be affecting the performance?

For instance, are objects created with object literal notation represented differently by the engine? I've seen noticeable changes in performance when merely adding or removing variables from an object, even if they weren't being used. Should the number of variables affect that?

Are there any other new developments in javascript (like Typed Arrays) that could have a big affect on performance?

And, finally, is there any good way to track performance due to intangibles like these? The profilers don't seem to help because the entire script with change, not just certain parts.

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I saw, that you create many closures (and directly execute them) for example in your UpdatePos method. The massive creation usage of closures as you do it may be a big performance problem.

I would recomment you to take a look at JavaScript optimization tools like Closure Compiler by Google http://closure-compiler.appspot.com/home I really can recomment using this with Advanced Optimization (but then you have to give him all you javascript code - otherwise or if you use eval you (might) get problems (because he renames not only local variables and deletes unused code))