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Difference between using Object as associative array in Flash AS3 and JavaScript

As I was porting a Roman number converter (I will post it shortly) I had written in JavaScript to AS3 and ran into an interesting "quirk" of the AS3 Object class. I doesn't keep the keys in the same order that they were declared. The code used an Object literal as an associative array; holding each roman "digit" along with it's decimal equivalent in descending order by value. I'd then use a for ... in loop to cycle through the object. In JavaScript I'd get the values in the same order they had been generated. AS3 seems to be a little more cavalier. The following code in Javascript:

var o = {
"name1":1,
"name2":1,
"name3":1,
"name4":1,
"name5":1
};
var a=0;
for (var n in o) {
document.write(" o " + a + ":"+n);
a++;
}

produces this result in all major browsers (Firefox 3.5, IE 8, Safari 4, Opera 9.54, Chrome 2):
o 0:name1 o 1:name2
o 2:name3
o 3:name4
o 4:name5

However, using the following code in the Flash IDE

var o:Object = {
"name1":1,
"name2":1,
"name3":1,
"name4":1,
"name5":1
};
var a:uint = 0
for (var n:String in o) {
trace(" o " + a + ":"+n);
a++;
}

resulted in the following trace result:
o 0:name4
o 1:name5
o 2:name1
o 3:name2
o 4:name3

Oddly, it seemed to produce the exact same order each time I ran it. I tried it with a Dictionary, to see if the made a difference, but results were similar. I tried different values, to try and find a reason for the ordering -- to no avail. If someone knows why it's consistently picks the same random order, I'd love to know.

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2009.08.16 11:25 PM | Permalink 0 Comments