"undefined" variables

hi,
i've been struggling with a little problem, i'd be very grateful for a straw to clutch at :-)

basically, i need to test a variable to see if it is undefined. i can test for NotaNumber easy enuf, but undefined is tricky.

the variable is compID, and if it is undefined, compID.length = 9 (9 letters in "undefined"!!! i was hoping it would be 0). however, comparing compID to "undefined" comes up false.

can anybody help a frazzled newbie web bloke?

cheers.

MonkeyBoy

The easiest thing to do I think is to set compID="testvalue" when you var it.

var compID="undefined";

or someother value that you know it will never get set to. Then you can test for that value

Hi monkeyboy:
Check out http://wsabstract.com/javatutors/determinevar.shtml ...I think it'll answer your question nicely.

thanks, time2brew.
unfortunately, i had to read the variable off the requesting URL using Request.QueryString, which meant that even if I had set up var compID with an initial value, it still comes back as undefined if there is no variable in the URL.
i case anyone is following this thread... :-))) ... i used a workaround which was to create a new string object with the value assigned as follows:
tempID = new String(Request.QueryString("compID")); // store as a string, so undefined = "undefined"
if (tempID == "undefined"){ //if no compID in URL
Session("Udata").newuser = 0;
}
else Session("Udata").newuser = 1;

the above nonsense actually stores the value of the variable retrieved from the URL request as the string "undefined", which can then be tested for.
phew!
bet there's a better way!!!!

thanks anyway, brew master!.

monkeyboy.


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<BLOCKQUOTE><font size="1" face="Verdana,Arial,Helvetica">quote:</font><HR>Originally posted by adashimar:
Hi monkeyboy:
Check out http://wsabstract.com/javatutors/determinevar.shtml ...I think it'll answer your question nicely.[/quote]

cool!
thanks adashimar, i think that might work a little more neatly than my solution... :-))

monkeyboy

why not use the nice method typeof?

if (typeof undefined_var == "undefined")
{
....
}