Bug in IIS 5.1 JScript - undefined strings from Request object

Robert Mark Bram · Oct 17, 2003

Hi All!

I have checked Windows Script help for the Undefined Data Type. It says I
should be able to do this:
// This method will work
if (typeof(x) == "undefined")
// do something

However, I have found that when I try to get something from Session and
Request that does not exist, the object coming back from each is different
when they should both be undefined.

My simple test:

<%@LANGUAGE="JAVASCRIPT" CODEPAGE="65001"%>
<html>
<body>
reallyNotThere: "<%= Session("reallyNotThere") %>" 
reallyNotThere2: "<%= Request("reallyNotThere2") %>" 
<%
var reallyNotThere = Session ("reallyNotThere");
Response.Write(" Not there "" + reallyNotThere + """)
if (typeof(reallyNotThere) == "undefined")
{
Response.Write(" it is not there!");
}
else
{
Response.Write(" it is there");
}

var reallyNotThere2 = Request("reallyNotThere2");
Response.Write(" Not there 2 "" + reallyNotThere2 +
""")
if (typeof(reallyNotThere2) == "undefined")
{
Response.Write(" it is not there!");
}
else
{
Response.Write(" it is there");
}
%>
</body>
</html>

The output:

reallyNotThere: ""
reallyNotThere2: ""

Not there "undefined"
it is not there!
Not there 2 "undefined"
it is there

If
(typeof(reallyNotThere) == "undefined")
is true, so should
(typeof(reallyNotThere2) == "undefined")

Rob

W d'Anjos · Oct 17, 2003

I think the difference is that Session("reallyNotThere") returns null
and Request("reallyNotThere2") returns an empty string.

Try Response.Write(typeof(reallyNotThere) + " - " +
typeof(reallyNotThere2)), if I am correct it should display "undefined
- object".

-Wagner

Robert Mark Bram · Oct 17, 2003

Hi Wagner,

I think the difference is that Session("reallyNotThere") returns null
and Request("reallyNotThere2") returns an empty string.

Try Response.Write(typeof(reallyNotThere) + " - " +
typeof(reallyNotThere2)), if I am correct it should display "undefined
- object".

Not quite - reallyNotThere2 is an object (with no toString method!) that
becomes the String "undefined" when you put in a String.

It seems an impossible test - it doesn't report itself as being null or
undefined plus it's not an empty String.. meaning there is no easy way to
tell whether it is "undefined" because it's not defined or "undefined"
because the user typed that... except if you test for this:
if ("toString" in reallyNotThere2)

I tried this:

var reallyNotThere = Session("reallyNotThere") ;
var reallyNotThere2 = Request("reallyNotThere") ;

Response.Write("========= "),
Response.Write("reallyNotThere== null - " + (reallyNotThere == null ) +
" ");
Response.Write("reallyNotThere === null - " + (reallyNotThere === null ) +
" ");
Response.Write("reallyNotThere2 == \"\" - " + (reallyNotThere2 == "" ) +
" ");
Response.Write("reallyNotThere2 === \"\" - " + (reallyNotThere2 === "" ) +
" ");
Response.Write("reallyNotThere2 == null - " + (reallyNotThere2 == null ) +
" ");
Response.Write("reallyNotThere2 === null - " + (reallyNotThere2 === null )
+ " ");
Response.Write(typeof(reallyNotThere) + " - " + typeof(reallyNotThere2)+
" "),
Response.Write("reallyNotThere is \"" + reallyNotThere + "\" - " +
"reallyNotThere2 is \"" + reallyNotThere2 + "\" ");
if ("toString" in reallyNotThere2) {
Response.Write("reallyNotThere2 has a toString ");
} else {
Response.Write("reallyNotThere2 has no toString ");
}
Response.Write("========= ");

Output:
=========
reallyNotThere== null - true
reallyNotThere === null - false
reallyNotThere2 == "" - false
reallyNotThere2 === "" - false
reallyNotThere2 == null - false
reallyNotThere2 === null - false
undefined - object
reallyNotThere is "undefined" - reallyNotThere2 is "undefined"
reallyNotThere2 has no toString
=========

Rob

Steve van Dongen · Oct 18, 2003

Hi Wagner,

Not quite - reallyNotThere2 is an object (with no toString method!) that
becomes the String "undefined" when you put in a String.

It seems an impossible test - it doesn't report itself as being null or
undefined plus it's not an empty String.. meaning there is no easy way to
tell whether it is "undefined" because it's not defined or "undefined"
because the user typed that... except if you test for this:
if ("toString" in reallyNotThere2)

I tried this:

var reallyNotThere = Session("reallyNotThere") ;
var reallyNotThere2 = Request("reallyNotThere") ;

I usually do this:
var reallyNotThere2 = String(Request("reallyNotThere"));
if (reallyNotThere2 == "" || reallyNotThere2 == "undefined")
reallyNotThere2 = null;
and then test for null where appropriate.

Regards,
Steve

Robert Mark Bram · Oct 19, 2003

Hi Steve!

I usually do this:
var reallyNotThere2 = String(Request("reallyNotThere"));
if (reallyNotThere2 == "" || reallyNotThere2 == "undefined")
reallyNotThere2 = null;
and then test for null where appropriate.

I don't like to use this because of the (admittedly remote) possibility that
I have a text field where "undefined" is a possible value... but I see your
point.

Rob

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Bug in IIS 5.1 JScript - undefined strings from Request object

Robert Mark Bram

W d'Anjos

Robert Mark Bram

Steve van Dongen

Robert Mark Bram

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