Subj : Re: undefined values
To   : netscape.public.mozilla.jseng
From : Martin Honnen <Martin.Honnen@t-online.de>
Date : Tue Aug 05 2003 03:02 pm



Matthias Thiel wrote:
> Hi,
> 
> is there a possibility to check, whether a variable is defined or not 
> (using SpiderMonkey) ?
> I tried out scripts like "x==undefined", but I got an error instead of true or false.
> With Rhino, such scripts are working and returning true or false. Is it a feature of Rhino ?

The usual check is
   if (typeof x == 'undefined')
However this doesn't allow you to distinguish the case where the 
variable is not defined at all and the case where the variable is 
defined with
   var x;
but not initialized.



-- 

	Martin Honnen
	http://JavaScript.FAQTs.com/

.