Strange output with my as3 arrays

Question

So, I think my question should be fairly straightforward, I am just looking for a little clarification on why I'm getting these seemingly odd results when I try to use the Array.indexOf method with null. Here's my code:

var myArray:Array = new Array(20);
trace(myarray.indexOf(null)); //output: -1
trace(myarray[0] == null); //output true

So, it looks like the elements of an array are defaulted to null when a length constructor parameter is initialized, but why does indexOf(null) not return 0?

I could be wrong but I think null is a tricky thing to work with, especially with such functions. I would try swapping the lines (i.e. tracing the condition before tracing the function) and seeing if it makes a difference. — puggsoy
– puggsoy, Commented Feb 10, 2013 at 7:36
@puggsoy, the output is the same regardless of the order the statements come in (I would hope that it would be... I would be disturbed if the == operator modified my array to make indexOf work somehow :P ) — Kreg
– Kreg, Commented Feb 10, 2013 at 8:06

loxxy · Accepted Answer · 2013-02-10 08:50:11Z

3

elements of an array are defaulted to null

Nope. It's a popular belief in JS & AS3. A property, when it has no definition, is undefined.

Besides, anyone implementing the indexOf function, would obviously check if the value to be searched is null before actually starting to search.

Also I think you are looking for this :

var myArray:Array = new Array(20);
trace(myArray.indexOf(undefined)); //output: 0
trace(myArray[0] == null); //output true

edited Feb 10, 2013 at 8:50

answered Feb 10, 2013 at 8:41

loxxy

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khailcs · Accepted Answer · 2013-02-10 13:28:33Z

2

If only a single numeric parameter is passed to the Array constructor, it is assumed to be length and it is converted to an integer by using the Integer() function. http://help.adobe.com/en_US/AS2LCR/Flash_10.0/help.html?content=00000737.html

var myArray:Array = new Array(20);
trace(myArray.length); //output: 20

As for the difference between null and undefined you can check this http://www.bobbyberberyan.com/2011/01/as3-undefined-vs-null/

answered Feb 10, 2013 at 13:28

khailcs

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1 Comment

Kreg Over a year ago

ooh, +1 for the null vs undefined link, I didn't realize as3 was so javascripty

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