Comments on: Don’t use Number to iterate over for-loops

By: Joel Berghoff

Joel Berghoff — Sun, 14 Jun 2009 18:07:17 +0000

I get slightly better results still if I use a prefix operator in the for-statement:
for (var i:uint = 0; i < length; ++i)

Is there a reason more people don’t do this?

By: Jacob Wright

Jacob Wright — Tue, 12 Aug 2008 22:51:44 +0000

Declaring a variable inside your loop statement or outside result in the same visibility and variable type. You wouldn’t get any performance gain doing it that way.

By: jwopitz

jwopitz — Wed, 30 Jul 2008 16:36:51 +0000

what kind of results would you get if you were to optimize further by saying this:

var i:uint;
var m:uint = someArray.length;
for (i; i < m; i++)
{ … }

I know that doesn’t remotely sound like a huge difference but I wonder if by establishing your variables outside the for loop if you get any further performance increases.

By: Keith Gaddis

Keith Gaddis — Thu, 24 Apr 2008 04:16:58 +0000

Bjarne Stroustrop used to say, “Premature optimization is the root of all evil.” I’m not sure in common use that the difference would be THAT significant, but all the same, good information to have!

By: Jacob Wright

Jacob Wright — Mon, 31 Mar 2008 16:59:26 +0000

The proof out there was what I linked to in the post. They were loops that were doing mathematical operations with the “i” variable. Using Number was faster in that scenario. This is less common then simply iterating over a loop.

I found that uint is ever-so-slightly faster than int and much faster than Number if you are simply iterating over a loop.

By: Jon Valliere

Jon Valliere — Tue, 25 Mar 2008 21:05:07 +0000

I also believe there is some proof out there that ‘uint’ is actually slower than ‘int’ for “for/while” iterations.

By: Andrew

Andrew — Thu, 20 Mar 2008 04:46:09 +0000

That’s funny. I was just wondering today which would be faster to use for iterating through arrays. I guess I guessed wrong.