Stupid JavaScript Trick of the Day: Variable Misdeclaration

Dear JavaScripters:

Laugh or cry depending on which side of the fence you are on.

I had a problem with an XMLHttpRequest object not working right.
readyState did not exist. Oh? Remember that I am still learning this
and am adapting code so there was the very real possibility that I had
overlooked something about setting up the object. It turned that that
I had overlooked something, just not something specific to the object.

I put in some checking to see the object variable's value and
nullness. Well, it did get assigned properly. Had I declared it
properly? Oh, yes.

OK, now what about where it is used? What? It is undefined?
Unfortunately, I had also declared it improperly.

It was supposed to be a global and was declared as such.
Unfortunately, I was following someone else's code so I did not notice
that I had also declared it locally in the function that set up the
object.

Happy Canada Day (July 1), Independence Day (July 4), some other
excuse for a good time (about now).

Sincerely,

Gene Wirchenko

In article <6d04v7hag5nipt5n8696rsp77d5bu0diop@4ax.com>,
Gene Wirchenko <genew@ocis.net> wrote:

> I had a problem with an XMLHttpRequest object not working right.
> readyState did not exist. Oh? Remember that I am still learning this
> and am adapting code so there was the very real possibility that I had
> overlooked something about setting up the object. It turned that that
> I had overlooked something, just not something specific to the object.
>
> I put in some checking to see the object variable's value and
> nullness. Well, it did get assigned properly. Had I declared it
> properly? Oh, yes.
>
> OK, now what about where it is used? What? It is undefined?
> Unfortunately, I had also declared it improperly.
>
> It was supposed to be a global and was declared as such.
> Unfortunately, I was following someone else's code so I did not notice
> that I had also declared it locally in the function that set up the
> object.

I take it that you only need one of these at once, then.

--
Tim

"That excessive bail ought not to be required, nor excessive fines imposed,
nor cruel and unusual punishments inflicted" -- Bill of Rights 1689

On Mon, 02 Jul 2012 22:52:47 +0100, Tim Streater
<timstreater@greenbee.net> wrote:

[snip]

>I take it that you only need one of these at once, then.

Yes, the global. It is the sort of mistake that I would not make
on my own, but when I do not fully understand the code that I am
adapting -- part of why I am adapting it -- errors can occur.

Sincerely,

Gene Wirchenko

On Tue, 03 Jul 2012 13:39:49 +0100, Tim Streater
<timstreater@greenbee.net> wrote:

>In article <6174v758q932srbnus4ghml7kssgkhpk6v@4ax.com>,
> Gene Wirchenko <genew@ocis.net> wrote:
>
>> On Mon, 02 Jul 2012 22:52:47 +0100, Tim Streater
>> <timstreater@greenbee.net> wrote:
>>
>> [snip]
>>
>> >I take it that you only need one of these at once, then.
>>
>> Yes, the global. It is the sort of mistake that I would not make
>> on my own, but when I do not fully understand the code that I am
>> adapting -- part of why I am adapting it -- errors can occur.
>
>OK. In my case I could have more than one httprequest running at once,
>so I left it as a variable local to my encapsulation function, thus:

I may change it. I am still experimenting.

[snip]

Sincerely,

Gene Wirchenko