That was my first thought. I ran the "slow loop" through the online compiler at:... | Hacker News

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asher on Nov 12, 2009 | parent | context | favorite | on: Google Closure: How not to write Javascript

That was my first thought. I ran the "slow loop" through the online compiler at:

http://closure-compiler.appspot.com/home

And whether I checked "Simple" or "Advanced" I got:

for(var a = 0;a < arr.length;a++)

So it's not optimizing that pattern yet.

jeff18 on Nov 12, 2009 [–]

It would have to determine that arr.length doesn't change during the loop. Pretty difficult problem. :)

gojomo on Nov 12, 2009 | [–]

I'm unsure if the smiley means you're being sarcastic, but if not:

Such determinations are a pretty common thing for an optimizing compiler to attempt:

http://en.wikipedia.org/wiki/Loop-invariant_code_motion

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