jsStruct: C-style struct reading in Javascript

Protip: I ramble a lot before getting to the link in question. You probably just want to jump straight to the project.

So in case you haven't picked up on it yet I tend to work with a lot of binary files in Javascript. This is, to put it kindly, an absolute mess. (I would put it unkindly, but this is a family friendly blog!)

Now, to the credit of the browser makers, binary parsing has certainly gotten a lot better in a very short period of time. When I was doing my Quake 2 and Quake 3 demos, the only way to parse binary was to request you file as a raw string from the server and use String.charCodeAt() to grab the bytes one by one and reconstruct them into the appropriate data types. This meant that parsing a float looked like this:

The somewhat depressing state of Object.create performance

I have recently been introduced to the niceties of the new EMCA 5 Object model, which revolves around Object.create. The syntax is a bit wonky to those of us that have been javascripting for some time now, but once you get used to it there are some really great features at work here, not the least of which are actual properties, a much better inheritance model, tighter access control, and more! I'm not crazy about losing the ability to "new" my objects, and the funny little hacks that you need to put in place to simulate a constructor are turn-offs for me, but past that there's an awful lot to love here...

... except the performance.

I was curious about how the new model compared with the tried and true methods in terms of speed, so I whipped up a simple jsperf benchmark to gauge how different aspects of the two object methodologies performed. (And I'm not the first either) The results, frankly, were rather depressing.

On my iMac with Chrome 14 (dev channel) new Obj() is currently outperforming Object.create() by a factor of 10! Seriously! 10 times slower, and we've lost constructor functions along the way! Fortunately member access and function calls are virtually indistinguishable performance-wise once the objects are created, which is good (if expected). Sadly, however, utilizing Properties (one of the big bonuses of the new model) is painfully slow. My tests showed a Property to be 200 time slower than a good old setFoo/getFoo pair. The numbers are about the same on Safari, though Firefox showed some interesting variations. There wasn't a single platform where the new model could be called a clear performance winner though.

Of course, the feature is fairly new and hasn't undergone the rigorous optimization that some of the older methods have, so I would fully expect to see these numbers improve moving forward, but for now if you're performance conscious you'd do well to steer clear of Object.create.

(Oh, and despite drastically redesigning the Javascript object model we STILL couldn't be bothered to add operator overloading? Really?!?)