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epanepucci-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2007-Apr-18 13:55 UTC

prototype / dom scope

Hi There,

First my environment:
   Firefox 2.0.0.3 on Linux (Extensions: Firebug, Webdeveloper,
Aardvark)


I have a webpage (XHTML 1.0 Transitional) in which after clicking on a
link,
I load a little <form> via Ajax.Updater.

The form contains buttons which when clicked will
call a javascript function defined in the initial webpage.

One of these JS functions is:

function enable_form_edit(aform) {

    alert(Prototype.Version);
    Form( aform ).enable();

}

the onclick which calls enable_form_edit() is:

    onclick="enable_form_edit($(this).up(''FORM''));"


The result is that the alert() actually displays the prototype version
that I have (1.5.1_rc2) but I get this error on my Firebug console:

>> Form is not a function
>>     Form(aform).enable();
which is pointing to the JS function above.

on the other hand, if in the enabe_form_edit() I have
    aform.enable();

then this works fine.


Questions:
   - why can''t I use "Form" as a singleton?
   - why is Prototype.Version available but not Form?

Thanks much!
Zac


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RobG

2007-Apr-19 05:54 UTC

head link

Re: prototype / dom scope

On Apr 18, 11:55 pm,
"epanepu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<epanepu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Hi There,
>
> First my environment:
>    Firefox 2.0.0.3 on Linux (Extensions: Firebug, Webdeveloper,
> Aardvark)
>
> I have a webpage (XHTML 1.0 Transitional) in which after clicking on a
> link,
> I load a little <form> via Ajax.Updater.
>
> The form contains buttons which when clicked will
> call a javascript function defined in the initial webpage.
>
> One of these JS functions is:
>
> function enable_form_edit(aform) {
>
>     alert(Prototype.Version);
>     Form( aform ).enable();
>
> }
>
> the onclick which calls enable_form_edit() is:
>
>    
onclick="enable_form_edit($(this).up(''FORM''));"
Consider:

      onclick="enable_form_edit(this.form);"

but if all the function does is enable the form, why not:

      onclick="$(this.form).enable();"

> The result is that the alert() actually displays the prototype version
> that I have (1.5.1_rc2) but I get this error on my Firebug console:
>
> >> Form is not a function
> >>     Form(aform).enable();
>
> which is pointing to the JS function above.
Because Form isn''t a function, it''s a plain object with some
properties.  Look at line 2548:

  var Form = {
     ...
  }

One of the properties added to the Form object is called
''enable'', it
is a function so you can use:

  Form.enable()


In Firefox and other browsers that allow the basic document elements
to be extended, all form objects in the document are extended with the
same properties as the Prototype Form object so in Firefox you can do:

 <form>
  <input type="button" onclick="alert(typeof
this.form.enable);"
    value="click">
 </form>

and you will see an alert with "function", but in IE you''ll
see
''undefined''.  So to be cross-browser you must do:

    onclick="alert(typeof $(this.form).enable);"
>
> on the other hand, if in the enabe_form_edit() I have
>     aform.enable();
>
> then this works fine.
Because the enable property is a reference to a function object, so
you can use the call operator with it.

> Questions:
>    - why can''t I use "Form" as a singleton?
Form is an object, it is not a function, using the call operator ()
with something other than a function will create a runtime error.

>    - why is Prototype.Version available but not Form?
Prototype is declared as a global object, it is assigned a property
called Version (among other things). When Prototype.Version is
evaluated, it returns whatever the value of Version has been set to.
The first couple of lines of Prototype.js:

  var Prototype = {
    Version: ''1.5.1_rc2'',
    ...
  }

so any time you like after the script element that loads Prototype.js
you can do alert(Prototype.Version) and you will see
''1.5.1_rc2'' (provided javascript is available and enabled).


--
Rob


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epanepucci-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2007-Apr-19 07:49 UTC

head link

Re: prototype / dom scope

> Because Form isn''t a function, it''s a plain object with
some
> properties.  Look at line 2548:
>
>   var Form = {
>      ...
>   }
I had seen that, but *Element* is declared just like *Form* and
Element(''blabla'').hide()
works.

This looks more like a bug, *all* of these extensions to the DOM are
usually
available as Singletons, and besides http://www.prototypejs.org/api/form/reset
gives an example using Form as a singleton.
> but if all the function does is enable the form, why not:
>
>       onclick="$(this.form).enable();"
It is not all it does, I was just being succint.

Anyways, thanks for the alternative workarounds.

Cheers,
   Zac



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RobG

2007-Apr-19 09:46 UTC

head link

Re: prototype / dom scope

On Apr 19, 5:49 pm,
"epanepu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<epanepu...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> > Because Form isn''t a function, it''s a plain object
with some
> > properties.  Look at line 2548:
>
> >   var Form = {
> >      ...
> >   }
>
> I had seen that, but *Element* is declared just like *Form* and
> Element(''blabla'').hide()
> works.
It does?  I get "Element is not a function", just like I get with
Form.
>
> This looks more like a bug, *all* of these extensions to the DOM are
> usually
> available as Singletons,
Maybe that''s causing confusion.  They aren''t
"extensions", they are
objects with properties.  Some (most?) of those properties are
references to function objects.  For Firefox et al, the base DOM
objects are extended with the same function objects.  For IE and
similar, they aren''t.

Don''t think of javascript as a classic object oriented language - it
isn''t, it''s *object based*.

> and besideshttp://www.prototypejs.org/api/form/reset
> gives an example using Form as a singleton.
The example is:

  Form.reset(''contact'')

which is using the reset property of the Form object which expects
either an ID or a form object as the parameter.   It is not attempting
to "call" the Form object like Form() which will produce a runtime
error.

Try:

  alert( typeof Form ) // shows object
  alert( typeof Form.reset ) // shows function
  alert( typeof Element ) // shows object
  alert( typeof Element.toggle ) // shows function

It would probably have been better if Prototype hadn''t named
it''s own
objects the same as other DOM and javascript objects. e.g. calling the
library ''Prototype.js'' causes plenty of confusion with those
trying to
learn about the javascript prototype property and object which are
totally different to the Prototype.js library and the Prototype object
declared within it.

>
> > but if all the function does is enable the form, why not:
>
> >       onclick="$(this.form).enable();"
>
> It is not all it does, I was just being succint.
Fine.  :-)

--
Rob


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epanepucci-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2007-Apr-19 11:14 UTC

head link

Re: prototype / dom scope

>The example is:
>
>   Form.reset(''contact'')
ahhhh! thank''s for clearly pointing that out... I feel like an idiot
now,
but better knowing than not.

Thanks again for wasting your time with me.

Cheers,
   Zac


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