What's the fastest way to get the Constructor of an Object in AS3?

Question

Which of these 3 is the fastest (least CPU cycles) on the AVM2 in ActionScript 3?

Object(instance).constructor

(instance as Object).constructor

instance["constructor"]

I would do some tests, but I have no idea how to accurately profile that kind of thing.

Answer 1

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performancetests.Constructors (5 iterations, 5,000,000 loops through each)                            
Player version: MAC 10,0,32,18 (debug)
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method...................................................ttl ms...avg ms
instanceAsObjectConstructor                                9516  1903.20
instanceBracketConstructor                                 6941  1388.20
objectDotConstructor                                       9916  1983.20
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I used Grant Skinner's AS3 Performance test harness and got these results.