[Zope] Zope and Javascript

[Passin, Tom]

> Behalf Of Asad Habib
> 
> Does anyone know of any resources that describe the use of 
> Javascript within Zope? In particular, I am trying to call a 
> Javascript function using the onChange event handler that is 
> tied to a HTML select element. I need this Javascript 
> function to perform an SQL query and then have it populate 
> another HTML select element with the result set. Is this 
> possible within Zope considering that queries are performed 
> by Z SQL methods and possible other factors that I am unaware 
> of? Any help would be greatly appreciated. Thanks.

A javascript function executed within a web page cannot influence
anything that Zope does, because by the time that the javascript
executes in the browser, Zope has alread finished producing the page.
The javascript action is local to the browser.

How you do it is to have your onChange handler submit a form to Zope.
That form should invoke a document, methods, etc., on Zope that will
construct the response you want (including any database access), and
return it to the browser.

Of course the new page will replace the old one, just as for any other
form submission.

If you do not want to replace the previous page, things get harder.  You
generally would use frames (possibly an Iframe), and send the form's
result to one of the other frames.  Then you would use javascript to
transfer the data from the frame that received it to the frame with the
re-populated select list.  The main problem here is to know when the
data has been completely received - of course you do not want to try to
transfer it before transmission is complete.

You can do this with the javascript equivalent of a wait command, but it
can be a bit tricky to get right.

Or, if you data set is not too large, you may be able to build
javascript data stsructures for all the relevant data in the original
page.  Then you can repopulate the select list without sending a form
back to the server.

Cheers,

Tom P