Status: New
Owner: ----
New issue 3144 by [email protected]: poor performance on property
lookup when the key is the result of a string concat
http://code.google.com/p/v8/issues/detail?id=3144
I know we should leave micro benchmarks to the VM implementers, and I am
sure some bugs/issues exist with my benchmark, but the performance
difference appears measurable, even in real scenarios.
I was able to get some noticeable improvements in some situations, by
avoiding this. Unfortunately, this isn't always practical/possible.
Summary:
```js
var KEY = 'fast_key';
var KEY_FROM_CONCAT = 'fast_' + 'key';
var obj = { };
obj[KEY] = 'foo';
obj[KEY_FROM_CONCAT] = 'foo';
obj[KEY] // will peform much faster then
obj[KEY_FROM_CONCAT] // <-- slower
```
simple runnable example:
https://gist.github.com/stefanpenner/ede92fbd00bf49bc5f09
benchmark: http://jsperf.com/lookup-key-length/2
It appears other runtimes, the various monkeys powering firefox, and
squirrels powering Safari's don't have incur this same penalty.
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