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From: RossGK on 25 Jun 2008 14:44
I'm a bit new to javascript - as will be obvious below.

I'm using an XMLHttpRequest to get a bit of data from server (django),
and it works nicely for single events. But my eventual outcome needs
to be a series of data transmissions. I figured requesting data over
and over until the data is some value that triggers the stop would be
an interesting first attempt. To move forward, I wrapped my initial
single data request in a for-loop to see if I could do multiple calls.

Here's my javascript stuff...

for (i=0;i<=5;i++) {
xmlHttp.onreadystatechange=function()

{ if (xmlHttp.readyState==4)
{ document.myForm.myvar.value=xmlHttp.responseText;
}
}
xmlHttp.open("GET","/ajax_data",true);
xmlHttp.send(null);

//alert("got here")
dopause(500); //wait 500ms
}

What I've noticed is that with that alert line commented out, nothing
seems to happen -ie I don't see the data receive. I expected to see
it flash 5 times (the server sends a random number)

When I put the alert in, the alert does in fact pop up, and the data
gets displayed.

Does the alert message cause a window refresh that I need to emulate
when the alert is not there. What do I need to do to make it cycle
through the get 5 times and actually show me what comes up, WITHOUT
using an alert pop!?

Thanks for any suggestions


From: after9 on 25 Jun 2008 15:27
On Jun 25, 2:44 pm, RossGK <ros...(a)gmail.com> wrote:
> I'm a bit new to javascript - as will be obvious below.
>
> I'm using an XMLHttpRequest to get a bit of data from server (django),
> and it works nicely for single events.  But my eventual outcome needs
> to be a series of data transmissions.  I figured requesting data over
> and over until the data is some value that triggers the stop would be
> an interesting first attempt.  To move forward, I wrapped my initial
> single data request in a for-loop to see if I could do multiple calls.
>
> Here's my javascript stuff...
>
>         for (i=0;i<=5;i++) {
>                 xmlHttp.onreadystatechange=function()
>
>                 { if (xmlHttp.readyState==4)
>                         { document.myForm.myvar.value=xmlHttp.responseText;
>                         }
>                 }
>                 xmlHttp.open("GET","/ajax_data",true);
>                 xmlHttp.send(null);
>
>                 //alert("got here")
>                 dopause(500);        //wait 500ms
>           }
>
> What I've noticed is that with that alert line commented out, nothing
> seems to happen -ie I don't see the data receive.  I expected to see
> it flash 5 times (the server sends a random number)
>
> When I put the alert in, the alert does in fact pop up, and the data
> gets displayed.
>
> Does the alert message cause a window refresh that I need to emulate
> when the alert is not there.  What do I need to do to make it cycle
> through the get 5 times and actually show me what comes up, WITHOUT
> using an alert pop!?
>
> Thanks for any suggestions

Wish I could test this, but I don't have the resources. I'm assuming
the myvar is a text field or text area in your form? Try appending
the responsetext to this section - not just setting it (not as a
permanent solution, mind you, but just to debug). It may be being
overwritten with a null response.
From: RossGK on 25 Jun 2008 15:44

> Wish I could test this, but I don't have the resources. I'm assuming
> the myvar is a text field or text area in your form?


Yes, the text gets assigned to myvar in the form below...

<form name="myForm">
Stuff: <input type="text" onkeyup="getServerData();" name="username" /
>
Response: <input type="text" name="myvar" />
</form>

.... and as I say works nicely in a single event, or with the alert
pop.

> Try appending the responsetext to this section - not just setting it (not as a
> permanent solution, mind you, but just to debug). It may be being
> overwritten with a null response.

Not sure what you mean... do you mean like some sort of print
statement? (sorry my javascript weakness is showing)....


From: after9 on 25 Jun 2008 15:46
On Jun 25, 3:44 pm, RossGK <ros...(a)gmail.com> wrote:
> > Wish I could test this, but I don't have the resources.  I'm assuming
> > the myvar is a text field or text area in your form?
>
> Yes, the text gets assigned to myvar in the form below...
>
> <form name="myForm">
>         Stuff: <input type="text" onkeyup="getServerData();" name="username" /
>
>         Response: <input type="text" name="myvar" />
> </form>
>
> ... and as I say works nicely in a single event, or with the alert
> pop.
>
> > Try appending the responsetext to this section - not just setting it (not as a
> > permanent solution, mind you, but just to debug).  It may be being
> > overwritten with a null response.
>
> Not sure what you mean... do you mean like some sort of print
> statement?  (sorry my javascript weakness is showing)....

Try document.myForm.myvar.value+=xmlHttp.responseText;

instead of

document.myForm.myvar.value=xmlHttp.responseText;
From: RossGK on 25 Jun 2008 16:02
On Jun 25, 3:46 pm, after9 <ggama...(a)gmail.com> wrote:
>
> Try document.myForm.myvar.value+=xmlHttp.responseText;
>
> instead of
>
> document.myForm.myvar.value=xmlHttp.responseText;

Same behaviour results. When I keep the alert box in there, I see the
data get appended successively to the the previous data, and the form
field fills up. Without the alert box, nothing shows up.

Looking at my server log, interestingly I notice each time the alert
pops up, the data is displayed and I dismiss the alert, the server
shows that it has received a request and sent the data.

Without the alert box, the server shows only one request (and nothing
shows up on my page). So it seems the for-loop doesn't succeed in
making multiple requests without the alert box.

Will have to puzzle over that a bit longer...
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