Error in script when checking version

Question

I'm placing some script in the form1::ready:form area and using JavaScript. I'm checking the version of Adobe Acrobat that is being used to lock folks out of using Acrobat 7.0 or earlier.
My script begins with:
var vappName = xfa.host.appType;
var vappVersion = xfa.host.version;
and uses the variable results to go through some if loops to hide and reveal things as appropriate. With these items at the beginning of my script, I get the error/warning message:
Script failed (language is javascript; context is xfa[0].form[0].form1[0])
Error: $host does not have property 'appType'
My code works as expected (hiding and revealing the proper items when I open the file in different versions of acrobat), so I'm not sure what the error is. I'm also using the same commands on a master page to fill in a text field with the version and type of software the user is using, and I get no errors there. Is the code in the wrong place?
If I replace the xfa.host.appType or xfa.host.version with text strings like:
var vappName = "Reader";
var vappVersion = 9;
then the code works as expected and has no errors, so there do not appear to be any problems with the if loops that follow.

Answer 1

1. Some JavaScript actions are not allowed to be executed until the form hasn't be initalized completely, like event.target.closeDoc(true); for example.
2. This was only a hint for you to avoid wasting time with programming different form actions depending of the users Reader version.
You can combine the version check with another action, like lauching the URL where the newest Reader can be downloaded.
That's very user friendly, I think.
if (typeof(app.viewerVersion) != "undefined")
if (app.viewerVersion < 9.0)
if(xfa.host.messageBox("Sorry, but this form requires Adobe Reader version 8.1 or higher!\rPress OK to close the form and download the newest version of Adobe Reader (freeware).\r\rThank you for your cooperation!", "Attention",1,0)==1)
event.target.closeDoc(true);
app.launchURL("http://get.adobe.com/de/reader/", true);