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anathema

2008-Feb-10 03:22 UTC

What if my element doesn''t exist yet

Newbie alert!

So let''s I have this in my javascript

Event.observe(''myLinkId'', ''onclick'',
myFunctionName);

or even

$(''myDivID'').hide

what if they don''t exist yet? For example i am pulling in content via
ajax.updater so some of my elements do not exist when the javascript
is loaded. So all my javascript fails and the page does not function
because it looks for those elements and does not find them.

So do i handle this?
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ESPNDev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2008-Feb-10 03:42 UTC

head link

Re: What if my element doesn''t exist yet

I''m not really sure how you''re code is set up, but the most
generic
way would be use setInterval and clearInterval when the condition is
met

IE

function setObservers(){
  if( $(''myLinkId'') ){
    Event.observe(''myLinkId'', ''onclick'',
myFunctionName);
    clearInterval(timer);
  }
}

var timer = setInterval(''setObservers'',100);

It''s not the most elegant solution, but w/o knowing exactly what
you''re trying to do, it''s the best i can offer.

On Feb 9, 7:22 pm, anathema
<spamfreeunive...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Newbie alert!
>
> So let''s I have this in my javascript
>
> Event.observe(''myLinkId'', ''onclick'',
myFunctionName);
>
> or even
>
> $(''myDivID'').hide
>
> what if they don''t exist yet? For example i am pulling in content
via
> ajax.updater so some of my elements do not exist when the javascript
> is loaded. So all my javascript fails and the page does not function
> because it looks for those elements and does not find them.
>
> So do i handle this?--~--~---------~--~----~------------~-------~--~----~
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anathema

2008-Feb-10 04:38 UTC

head link

Re: What if my element doesn''t exist yet

Well let me give you a little better explanation.

initially a page is loaded... let''s say the home page. from there
people use the main navigation. when a link is clicked i get the page
through ajax.update with fancy fades and stuff.

all is good because that nav exists on every page so the elements are
always present. however, on one of the ''pages'' that i retrieve
via
ajax there is a sub nav. so now i have all these new elements in which
i want to do the same thing as i did the main nav. click on link and
content is replaced.

did that make sense?



On Feb 9, 7:42 pm, "ESPN...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<ESPN3.DL-
Community...-xX8xgfAcNKEAvxtiuMwx3w@public.gmane.org>
wrote:> I''m not really sure how you''re code is set up, but the
most generic
> way would be use setInterval and clearInterval when the condition is
> met
>
> IE
>
> function setObservers(){
>   if( $(''myLinkId'') ){
>     Event.observe(''myLinkId'',
''onclick'', myFunctionName);
>     clearInterval(timer);
>   }
>
> }
>
> var timer = setInterval(''setObservers'',100);
>
> It''s not the most elegant solution, but w/o knowing exactly what
> you''re trying to do, it''s the best i can offer.
>
> On Feb 9, 7:22 pm, anathema
<spamfreeunive...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > Newbie alert!
>
> > So let''s I have this in my javascript
>
> > Event.observe(''myLinkId'',
''onclick'', myFunctionName);
>
> > or even
>
> > $(''myDivID'').hide
>
> > what if they don''t exist yet? For example i am pulling in
content via
> > ajax.updater so some of my elements do not exist when the javascript
> > is loaded. So all my javascript fails and the page does not function
> > because it looks for those elements and does not find them.
>
> > So do i handle this?--~--~---------~--~----~------------~-------~--~----~
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Nathan Nobbe

2008-Feb-10 04:41 UTC

head link

Re: What if my element doesn''t exist yet

On Feb 9, 2008 10:22 PM, anathema
<spamfreeuniverse-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> Newbie alert!
>
> So let''s I have this in my javascript
>
> Event.observe(''myLinkId'', ''onclick'',
myFunctionName);
>
> or even
>
> $(''myDivID'').hide
>
> what if they don''t exist yet? For example i am pulling in content
via
> ajax.updater so some of my elements do not exist when the javascript
> is loaded. So all my javascript fails and the page does not function
> because it looks for those elements and does not find them.
>
> So do i handle this?

first off you should be using dom level 2 events; so onclick should be
click.
second, if the element w/ id, myLinkId, doesnt exist until its placed in the
dom by Ajax.Updater, then simply include it in a script tag in the response
from the server,
<script>
Event.observe(''myLinkId'', ''click'',
myFunctionName);
</script>
then set evalScripts:true in the Ajax.Options when you instantiate
Ajax.Updater
and you should be good to go ;)

-nathan

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ESPNDev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org

2008-Feb-10 05:55 UTC

head link

Re: What if my element doesn''t exist yet

Yup. That makes sense. So what you want to do is not call
Event.observe on page load but, after the Ajax call has been completed
and the html inserted.

You may not be able to use the updater method, since you need to
coordinate the call.

Instead, use Ajax.Request and manually update the subnav with the $
(''container'').update(html) method. After that, THEN call
Event.Observe.

On Feb 9, 8:38 pm, anathema
<spamfreeunive...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> Well let me give you a little better explanation.
>
> initially a page is loaded... let''s say the home page. from there
> people use the main navigation. when a link is clicked i get the page
> through ajax.update with fancy fades and stuff.
>
> all is good because that nav exists on every page so the elements are
> always present. however, on one of the ''pages'' that i
retrieve via
> ajax there is a sub nav. so now i have all these new elements in which
> i want to do the same thing as i did the main nav. click on link and
> content is replaced.
>
> did that make sense?
>
> On Feb 9, 7:42 pm,
"ESPN...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org"
<ESPN3.DL-Community...-xX8xgfAcNKEAvxtiuMwx3w@public.gmane.org> wrote:
> > I''m not really sure how you''re code is set up, but
the most generic
> > way would be use setInterval and clearInterval when the condition is
> > met
>
> > IE
>
> > function setObservers(){
> >   if( $(''myLinkId'') ){
> >     Event.observe(''myLinkId'',
''onclick'', myFunctionName);
> >     clearInterval(timer);
> >   }
>
> > }
>
> > var timer = setInterval(''setObservers'',100);
>
> > It''s not the most elegant solution, but w/o knowing exactly
what
> > you''re trying to do, it''s the best i can offer.
>
> > On Feb 9, 7:22 pm, anathema
<spamfreeunive...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > > Newbie alert!
>
> > > So let''s I have this in my javascript
>
> > > Event.observe(''myLinkId'',
''onclick'', myFunctionName);
>
> > > or even
>
> > > $(''myDivID'').hide
>
> > > what if they don''t exist yet? For example i am pulling
in content via
> > > ajax.updater so some of my elements do not exist when the
javascript
> > > is loaded. So all my javascript fails and the page does not
function
> > > because it looks for those elements and does not find them.
>
> > > So do i handle this?--~--~---------~--~----~------------~-------~--~----~
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Nathan Nobbe

2008-Feb-10 06:12 UTC

head link

Re: What if my element doesn''t exist yet

On Feb 10, 2008 12:55 AM, ESPNDev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
<ESPN3.DL-CommunityDev-xX8xgfAcNKEAvxtiuMwx3w@public.gmane.org>
wrote:
>
> Yup. That makes sense. So what you want to do is not call
> Event.observe on page load but, after the Ajax call has been completed
> and the html inserted.
>
> You may not be able to use the updater method, since you need to
> coordinate the call.
>
> Instead, use Ajax.Request and manually update the subnav with the $
> (''container'').update(html) method. After that, THEN call
> Event.Observe.

using Ajax.Updater together w/ the evalScripts option will do just that,
and it will be simpler to implement.

-nathan

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Nicolás Sanguinetti

2008-Feb-10 08:27 UTC

head link

Re: What if my element doesn''t exist yet

Or, you could add to the onComplete handler on the Ajax.Updater

new Ajax.Updater(container, url, {
  onComplete: function(t) { $("link").observe("click",
handler); }
});

This will keep the javascript in one place, and will be called only
after the content has been pulled into the page.

Get to know all the callbacks and options you can pass to the
Ajax.Request and Ajax.Updater objects:
http://prototypejs.org/api/ajax/options

Best,
-Nicolas

On Feb 10, 2008 4:12 AM, Nathan Nobbe
<quickshiftin-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> On Feb 10, 2008 12:55 AM, ESPNDev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
> <ESPN3.DL-CommunityDev-xX8xgfAcNKEAvxtiuMwx3w@public.gmane.org>
wrote:
>
> >
> > Yup. That makes sense. So what you want to do is not call
> > Event.observe on page load but, after the Ajax call has been completed
> > and the html inserted.
> >
> > You may not be able to use the updater method, since you need to
> > coordinate the call.
> >
> > Instead, use Ajax.Request and manually update the subnav with the $
> > (''container'').update(html) method. After that, THEN
call
> > Event.Observe.
>
> using Ajax.Updater together w/ the evalScripts option will do just that,
>  and it will be simpler to implement.
>
> -nathan
>
>
>
>  >
>
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kangax

2008-Feb-10 14:30 UTC

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Re: What if my element doesn''t exist yet

Or you could use event delegation which doesn''t really care if element
exists.
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Nathan Nobbe

2008-Feb-10 17:25 UTC

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Re: What if my element doesn''t exist yet

On Feb 10, 2008 9:30 AM, kangax
<kangax-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> Or you could use event delegation which doesn''t really care if
element
> exists.

are you suggesting to use the custom events in 1.6.0 whereby the original
page load would observe an (custom) event that would then be fired by the
Ajax.Updater?

or have i completely missed the boat :)?

-nathan

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anathema

2008-Feb-10 21:41 UTC

head link

Re: What if my element doesn''t exist yet

Thanks for all the replies, although I don''t know how to go about
implementing some of them.

What is event delegation?


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kangax

2008-Feb-10 22:46 UTC

head link

Re: What if my element doesn''t exist yet

Event delegation is a technique of observing events on an ancestor
element (positioned "higher" in DOM) and exploiting events''
bubbling
nature (ability of ancestor to catch event originated on its
descendant). It all just sounds complicated but essentially means
this:

document.observe(''click'', function(e) {
  if (e.findElement(''#myLinkId'')) myFunction(e);
})

Now myFunction will be called only if user clicks on an element with
specified id (and simply ignoring everything else)

Hope this helps.

Best,
kangax
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anathema

2008-Feb-10 23:44 UTC

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Re: What if my element doesn''t exist yet

this is probably going to sound stupid, but what the ''e''
represent?


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Nathan Nobbe

2008-Feb-11 00:17 UTC

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Re: What if my element doesn''t exist yet

On Feb 10, 2008 6:44 PM, anathema
<spamfreeuniverse-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> this is probably going to sound stupid, but what the ''e''
represent?

if you are talking about the code kangax posted,
document.observe(''click'', function(e) {
 if (e.findElement(''#myLinkId'')) myFunction(e);
})
the function in the second argument to document.observe() is anonymous.
its designed to be called at a later point in time.  when it does get
called,
it will get a reference passed to it, an event, thats what e is in this
case.

-nathan

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anathema

2008-Feb-11 00:52 UTC

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Re: What if my element doesn''t exist yet

Sorry, I don''t get it. Does it have to be an ''e'', or
did he just
choose that letter randomly? Maybe a complete example would help.
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Gareth Evans

2008-Feb-11 01:07 UTC

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Re: What if my element doesn''t exist yet

the e is the argument name on the function and what the event object becomes
known as within the scope of the function. it can be anything, but most of
us use ''e'' as it''s short and then you can copy/paste
code easily.
if you prefer you can call it evt or something..
prototype passes the event object as that argument to the function, like
this:

definition:
function dosomething(somearg)
{
 alert(somearg)
}

call:
dosomething(''hi'');

function arguments in scope:
somearg => "hi"

output:
alert box of "hi"

if you take this example and treat somearg as e and "hi" as an event
object.. the same applies

On Feb 11, 2008 1:52 PM, anathema
<spamfreeuniverse-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> Sorry, I don''t get it. Does it have to be an
''e'', or did he just
> choose that letter randomly? Maybe a complete example would help.
> >
>
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Rails spinoffs - Feb 2008 - What if my element doesn't exist yet

What if my element doesn''t exist yet

Re: What if my element doesn''t exist yet

Re: What if my element doesn''t exist yet

Re: What if my element doesn''t exist yet

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Re: What if my element doesn''t exist yet

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