jQuery Forum

It has less to do with RegExps and more to do with inline objects. You'll note that I also moved inline functions out and declared them above. I'd, eventually, like to do the same with inline arrays and object literals. RegExp, Function, Array, and Objects shouldn't be re-declared on every function call (or on every iteration in a loop!).
While very-simple RegExp optimizations may be a wash, performance-wise, (I note that your test regexp is only against a couple characters and doesn't even use a capturing expression) the code simplification and minification benefits are very real. Going through this process I was able to remove a large number of duplicate RegExp - and that's always a good thing.
<br clear="all">--John

<div>You're right, the regexps was too simple. I updated the test with longer and more complex expression and the time is still the same.</div><div>
</div>I agree about caching regexps that are re-used in many places, obviously. Not so much about one-time expressions or strings.<div>
I'm really aware of how the different interpreters work, but it seems to me that immutable literals (strings, numbers, regexps) are the first thing I'd cache in a constant. Maybe current interpreters do that already internally ?

2009/7/20 Ariel Flesler <aflesler@gmail.com>:

You need to be careful with your testing. Executing a function which has the regexp will result in non-deterministic results (the function call itself will probably take longer to run than the actual regexp being executed).
A revised test:
<a href="http://dev.jquery.com/~john/test/regexp.html">http://dev.jquery.com/~john/test/regexp.html</a>
Results (New vs. Old):
FF 3.5   123ms  119ms
SF 4.0      8ms     11ms
IE 6.0    220ms  490ms
As you can see, the new engines do optimize this quite well - but Internet Explorer is definitely a different matter.
<br clear="all">--John

I ran it around 15 times and the winner changes radically, both yield random numbers between 40-80 in Chrome.<div>Non-caching seems to win most of the time but with the change rate, the numbers don't seem reliable.</div>
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<div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="gmail_quote"><div class="im"><blockquote class="gmail_quote" style="border-left:1px solid rgb(204, 204, 204);margin:0pt 0pt 0pt 0.8ex;padding-left:1ex">
I ran it around 15 times and the winner changes radically, both yield random numbers between 40-80 in Chrome.<div>
Non-caching seems to win most of the time but with the change rate, the numbers don't seem reliable.</div></blockquote></div><div>
I assume you're talking about Internet Explorer 6? You need to use a copy that has a reliable timer, in order to get reliable timer results.</div>
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</div><div>No, Chrome last version.</div></div>--
Ariel Flesler
<a href="http://flesler.blogspot.com">http://flesler.blogspot.com</a>

<div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><div class="gmail_quote"><div>No, Chrome last version.</div></div></blockquote>
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With the modern browsers and their JIT engines (Chrome, Safari, FF 3.5) the results to micro-benchmarks are going to be anyone's guess (since they'll be optimized so heavily - it's likely that the results will be at the mercy of the operating system and what else is running, rather than the performance of the browser itself).
--John
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2009/7/20 John Resig <jeresig@gmail.com>:

Nick Fitzsimons