Object Sealing Benefits?

Hi Ashley,

I was just reading this page recently and was wondering as to how much benefit that sealed objects bring. I found and ran a test here on JSPerf, and what I'm seeing is that in fact the extra security actually SLOWS down the property access. Let me know what you think.

Chrome really suffer a lot of performance with the example or test method.

Yeah, we actually turned off object sealing in the runtime a long time ago because it had a pretty big performance impact on some systems. I've removed that section from the SDK manual now. Still though it's a good idea performance-wise to pretend the objects are sealed, because JS engines can't optimise well for objects with dynamic properties - create all properties you need in onCreate and only use those in your code.

Good to know, thanks.

Edit: Though, it does occur to me to note that C2 recycles the object instances, and most likely only clears all properties (hopefully, instead of deleting them), so in effect, properties set should never be set again in practice (so no dynamic issues to worry about).