So I’m writing this Flex widget/app/thingy that will let people vote for things on my site. I need to test that the user has selected one of the radio buttons when they hit the submit vote button. The code for that is:

Pretty simple stuff. In the if-statement I’m essentially saying, “if votingChoices.selectedValue DOESN’T exist then do this stuff, else do this other stuff.

Like I said, simple. Right?

But there’s a catch. I wasn’t paying attention and gave the radioButtons data values of, wait for it, numbers starting with zero. And you know what that means: no one will be able to submit the first choice in the list.

Okay, so simple fix. I shouldn’t use numbers, especially starting with zero, for the radioButton values.

But better yet I could just change the if-statement to:

if( votingChoices.selectedValue == null ) { ...

That would be the smart thing to do. And I tell myself that all the time. Don’t test for the existence of something in an if statement by just placing a reference. Go ahead and write out undefined or null. Because that’s what you’re really testing.

I can’t count the number of times I’ve screwed that up. So now every time I do that I’ll force myself to come back to this post and comment that no I can’t learn from my mistakes. :-)

So here are a few other things that equate to false. From Moock’s Essential ActionScript 3.0.

Here is a table of the default values for the various types.