Timing of JavaScript blocks

D

DrKen

Sorry to be asking so many questions (and no, I don't expect anyone to
go back and look at what I wrote before--that wasn't what I was
saying) but I'm going beyond what my big, fat Beginning JavaScript
book says.

I am required to add a script block just before the closing </body>
tag. This small script needs to be able to use the value of a form
field that is hidden (and gets its value through a special tag from
the database on the fly). I'm trying to figure out if the hidden
value will be available before this script block, that is all CDATA is
executed or if I need to do something to make sure the hidden value is
set first and then the block at the bottom of the HTML is executed.
Since, as I learned in a previous answer from the group, the script
blocks are executed in the order they occur (apart from event handlers
like onChange calling functions), I'm hoping it is safe to assume a
script block at the bottom won't be processed until after the page is
loaded and the hidden fields are filled in. Is that a correct
assumption? Thanks.

Ken
 
T

Tim Streater

DrKen said:
Sorry to be asking so many questions (and no, I don't expect anyone to
go back and look at what I wrote before--that wasn't what I was
saying) but I'm going beyond what my big, fat Beginning JavaScript
book says.

I am required to add a script block just before the closing </body>
tag.
Required?

This small script needs to be able to use the value of a form
field that is hidden (and gets its value through a special tag from
the database on the fly). I'm trying to figure out if the hidden
value will be available before this script block, that is all CDATA is
executed or if I need to do something to make sure the hidden value is
set first and then the block at the bottom of the HTML is executed.
Since, as I learned in a previous answer from the group, the script
blocks are executed in the order they occur (apart from event handlers
like onChange calling functions), I'm hoping it is safe to assume a
script block at the bottom won't be processed until after the page is
loaded and the hidden fields are filled in. Is that a correct
assumption? Thanks.
Click to expand...

I wouldn't make assumptions like that. You should use something like:

<body onload="yourscript();">

Then you'll know that your script doesn't run until the whole of the
page is loaded [1]. It also then won't matter where yourscript() is
located within the page.

Timing is important with this stuff. I'd be inclined to put all code
into functions except for declaring globals (if you have any), and
initialise those in your onload function. Then all your code is executed
when events fire and your donkeymentation should describe when that is.

[1] IIRC, there are some wrinkles about what "loaded" means, e.g. are
all images rendered before this event fires ...
 
D

DrKen

 DrKen said:
Sorry to be asking so many questions (and no, I don't expect anyone to
go back and look at what I wrote before--that wasn't what I was
saying) but I'm going beyond what my big, fat Beginning JavaScript
book says.
Click to expand...
I am required to add a script block just before the closing </body>
tag.
Required?

This small script needs to be able to use the value of a form
field that is hidden (and gets its value through a special tag from
the database on the fly).  I'm trying to figure out if the hidden
value will be available before this script block, that is all CDATA is
executed or if I need to do something to make sure the hidden value is
set first and then the block at the bottom of the HTML is executed.
Since, as I learned in a previous answer from the group, the script
blocks are executed in the order they occur (apart from event handlers
like onChange calling functions), I'm hoping it is safe to assume a
script block at the bottom won't be processed until after the page is
loaded and the hidden fields are filled in.  Is that a correct
assumption? Thanks.
Click to expand...

I wouldn't make assumptions like that. You should use something like:

<body onload="yourscript();">

Then you'll know that your script doesn't run until the whole of the
page is loaded [1]. It also then won't matter where yourscript() is
located within the page.

Timing is important with this stuff. I'd be inclined to put all code
into functions except for declaring globals (if you have any), and
initialise those in your onload function. Then all your code is executed
when events fire and your donkeymentation should describe when that is.

[1] IIRC, there are some wrinkles about what "loaded" means, e.g. are
all images rendered before this event fires ...

--
Tim

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

Thanks Tim. In further experimenting, I have a further question about
onload() vs. script parsing.

I am required to add the following script block to my page and am
supposed to put it as close to the bottom of the page as possible,
like just before the </body> tag.

<script type="text/javascript">
//<![CDATA[
s.channel="Admissions";
s.pageName="Applications: Graduate: Start";
s.hier1="applications,graduate";
alert("omniIdentifier: " + omniIdentifier);
s.events="event8:GRAD"+ "TEST" + omniIdentifier;
//]]>
</script>

I set the value of omniIdentifer in a function fired at onload time.
The variable is defined near the top of the file:
<script type="text/javascript">
var omniIdentifier = null;
</script>
The function is defined after the </form> element:

<script LANGUAGE = JavaScript>
// <!--Code to support Omniture -->
// Added for SSD-245
function getOmniIdentifierOnLoad()
{
omniIdentifier = document.getElementById("omniEmail").value;
return true;
}
</script>

This code must run before the CDATA block I was given. onload doesn't
seem to run until after all the script parsing and such has taken
place. How can I, as it were, beat the execution of the JavaScript at
the bottom of the page. Right now, my alert() shows that the value I
want is null. Thanks.

Ken
 
T

Tim Streater

DrKen said:
I am required to add the following script block to my page and am
supposed to put it as close to the bottom of the page as possible,
like just before the </body> tag.

<script type="text/javascript">
//<![CDATA[
s.channel="Admissions";
s.pageName="Applications: Graduate: Start";
s.hier1="applications,graduate";
alert("omniIdentifier: " + omniIdentifier);
s.events="event8:GRAD"+ "TEST" + omniIdentifier;
//]]>
</script>

I set the value of omniIdentifer in a function fired at onload time.
The variable is defined near the top of the file:
<script type="text/javascript">
var omniIdentifier = null;
</script>
The function is defined after the </form> element:

<script LANGUAGE = JavaScript>
// <!--Code to support Omniture -->
// Added for SSD-245
function getOmniIdentifierOnLoad()
{
omniIdentifier = document.getElementById("omniEmail").value;
return true;
}
</script>

This code must run before the CDATA block I was given. onload doesn't
seem to run until after all the script parsing and such has taken
place. How can I, as it were, beat the execution of the JavaScript at
the bottom of the page. Right now, my alert() shows that the value I
want is null. Thanks.
Click to expand...

Why don't you make that code be a function. Then you control when it's
executed:

<script type="text/javascript">
//<![CDATA[
function andFinally ()
{
s.channel="Admissions";
s.pageName="Applications: Graduate: Start";
s.hier1="applications,graduate";
alert("omniIdentifier: " + omniIdentifier);
s.events="event8:GRAD"+ "TEST" + omniIdentifier;
}
//]]>
</script>

Then you've got :

<body onload="yourscript();">

and finally:

function yourscript ()
{
getOmniIdentifierOnLoad();
andFinally ();
}

That way it's OK if for some reason your CDATA block needs to be
physically near the end of the page.
 
D

DrKen

<ae745872-ef67-41d1-bd2a-655ddbbfe...@d26g2000prn.googlegroups.com>,
Click to expand...
I wouldn't make assumptions like that. You should use something like:
Click to expand...
<body onload="yourscript();">
Click to expand...
Then you'll know that your script doesn't run until the whole of the
page is loaded [1]. It also then won't matter where yourscript() is
located within the page.
Click to expand...
Timing is important with this stuff. I'd be inclined to put all code
into functions except for declaring globals (if you have any), and
initialise those in your onload function. Then all your code is executed
when events fire and your donkeymentation should describe when that is.
Click to expand...
[1] IIRC, there are some wrinkles about what "loaded" means, e.g. are
all images rendered before this event fires ...
"That excessive bail ought not to be required, nor excessive fines imposed,
nor cruel and unusual punishments inflicted"  --  Bill of Rights 1689
Click to expand...

Thanks Tim.  In further experimenting, I have a further question about
onload() vs. script parsing.

I am required to add the following script block to my page and am
supposed to put it as close to the bottom of the page as possible,
like just before the </body> tag.

<script type="text/javascript">
//<![CDATA[
        s.channel="Admissions";
        s.pageName="Applications: Graduate: Start";
        s.hier1="applications,graduate";
        alert("omniIdentifier: " + omniIdentifier);
        s.events="event8:GRAD"+ "TEST" + omniIdentifier;
//]]>
</script>

I set the value of omniIdentifer in a function fired at onload time.
The variable is defined near the top of the file:
<script type="text/javascript">
        var omniIdentifier = null;
        </script>
The function is defined after the </form> element:

<script LANGUAGE = JavaScript>
// <!--Code to support Omniture  -->
// Added for SSD-245
        function getOmniIdentifierOnLoad()
        {
          omniIdentifier = document.getElementById("omniEmail").value;
          return true;
        }
</script>

This code must run before the CDATA block I was given.  onload doesn't
seem to run until after all the script parsing and such has taken
place.  How can I, as it were, beat the execution of the JavaScript at
the bottom of the page.  Right now, my alert() shows that the value I
want is null.  Thanks.

Ken- Hide quoted text -

- Show quoted text -
Click to expand...

I've been able to make this work, at least so far as I can tell
running the page by itself in Firefox, using a function invoked from
onload(). It looks to me like JS script blocks are executed, except
of course functions, before the page is loaded, at least in FF. I
don't know if this is true in all browsers but since I've put all the
relevant code into a function, it seems to be okay. Thanks for the
help.


Ken
 
D

Dr J R Stockton

In comp.lang.javascript message <ae745872-ef67-41d1-bd2a-655ddbbfe336@d2
6g2000prn.googlegroups.com>, Wed, 22 Jun 2011 13:37:40, DrKen
Sorry to be asking so many questions (and no, I don't expect anyone to
go back and look at what I wrote before--that wasn't what I was
saying) but I'm going beyond what my big, fat Beginning JavaScript
book says.

I am required to add a script block just before the closing </body>
tag. This small script needs to be able to use the value of a form
field that is hidden (and gets its value through a special tag from
the database on the fly). I'm trying to figure out if the hidden
value will be available before this script block, that is all CDATA is
executed or if I need to do something to make sure the hidden value is
set first and then the block at the bottom of the HTML is executed.
Since, as I learned in a previous answer from the group, the script
blocks are executed in the order they occur (apart from event handlers
like onChange calling functions), I'm hoping it is safe to assume a
script block at the bottom won't be processed until after the page is
loaded and the hidden fields are filled in. Is that a correct
assumption? Thanks.
Click to expand...

(1) Be aware that, when a page is reloaded in Firefox 3 after the user
has altered an input control, and after the page source has been edited,
then the value of the control is not lost (unless the value in the
source was changed) - but may seem to be moved if the controls no longer
appear in the same order. It can be very useful in testing, but might
conceivably affect your situation.

(2) On the whole, I agree with Tim.

(3) You could, perhaps, add another hidden field, at the end of the page
and set last, and not read the other hidden fields until the new field
had been set to a magic value. Caveat (1).

(Z) Different newsreaders display things differently. Do not assume
that readers of an article will necessarily notice who wrote it, unless
a sufficiently full real-type name is given in the body of the article,
or you use a distinctive delimited sig.
 

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