Javascript Switch

Dennis M. Marks

I have a javascript that displays the site contents and it is included
in every one of my pages. It has logic that makes it work a little
differently in the home page.

Currently I check the page title and if it the home page title I do one
thing otherwise I do another. I wanted to add a translator for the page
which changes the page title.

I would like to get away from using the page title as a check because
of this. I have tried placing a global variable in a separate script on
the home page and it works fine for the home page. The problem is that
it is undefined on the other pages.

Is there a way to check for the presence of a variable without giving
an error if not there? I don't want to define it on every page unless I
have to.

BTW: If I have a script like this: <script src="xxx"
type="text/javascript">some code</script>. Will "some code" be
processed before source code, after source code, or not at all. Is it
consistant on all browsers?

--
Dennis M. Marks
http://www.dcs-chico.com/~denmarks/
Replace domain.invalid with dcsi.net
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Jul 20 '05 #1

Subscribe Post Reply

1593

Mike

> Is there a way to check for the presence of a variable without giving

an error if not there? I don't want to define it on every page unless I
have to.
Use the typeof operator to check and see if your variable is defined.

example:

if (typeof(myVar) != 'undefined'){
//do processing
}

BTW: If I have a script like this: <script src="xxx"
type="text/javascript">some code</script>. Will "some code" be
processed before source code, after source code, or not at all. Is it
consistant on all browsers?

All browsers as far as I know parse the document in top down order. So if
you want some script to execute before the HTML source is parsed simply
place the script block above the <html> tag.

Regards
Mike

Jul 20 '05 #2

Cenekemoi

Bonjour à Mike <no****@please.com> qui nous a écrit :

Is there a way to check for the presence of a variable without giving
an error if not there? I don't want to define it on every page
unless I have to.

Use the typeof operator to check and see if your variable is defined.

example:

if (typeof(myVar) != 'undefined'){
//do processing
}

Better (IMHO) :

if (typeof(window['myVar') != 'undefined'){
//do processing
}

--
Cordialement, Thierry ;-)

Jul 20 '05 #3

Michael Winter

On Thu, 04 Mar 2004 07:09:47 -0800, Dennis M. Marks
<de******@domain.invalid> wrote:

[snip]

Is there a way to check for the presence of a variable without
giving an error if not there? I don't want to define it on every
page unless I have to.
function isDefined( ref ) {
return 'undefined' != typeof ref;
}
...
if( isDefined( aVariable )) {
...
}
BTW: If I have a script like this: <script src="xxx"
type="text/javascript">some code</script>. Will "some code" be
processed before source code, after source code, or not at all. Is
it consistant on all browsers?

If you specify the source attribute, there should be nothing within the
element. From the HTML 4.01 Specification, Section 18.2.1 - The SCRIPT
element:

"If the src attribute is not set, user agents must interpret the
contents of the element as the script. If the src has a URI value,
user agents must ignore the elementâ€™s contents and retrieve the
script via the URI."

Mike

--
Michael Winter
M.******@blueyonder.co.invalid (replace ".invalid" with ".uk" to reply)

Jul 20 '05 #4

Randy Webb

Dennis M. Marks wrote:

I have a javascript that displays the site contents and it is included
in every one of my pages. It has logic that makes it work a little
differently in the home page.

Currently I check the page title and if it the home page title I do one
thing otherwise I do another. I wanted to add a translator for the page
which changes the page title.

I would like to get away from using the page title as a check because
of this. I have tried placing a global variable in a separate script on
the home page and it works fine for the home page. The problem is that
it is undefined on the other pages.
Check window/document.location.href and the title won't matter.

Is there a way to check for the presence of a variable without giving
an error if not there? I don't want to define it on every page unless I
have to.

BTW: If I have a script like this: <script src="xxx"
type="text/javascript">some code</script>. Will "some code" be
processed before source code, after source code, or not at all. Is it
consistant on all browsers?

Not at all unless the browser doesn't understand the src attribute.
--
Randy
Chance Favors The Prepared Mind
comp.lang.javascript FAQ - http://jibbering.com/faq/

Jul 20 '05 #5

Dennis M. Marks

In article <c2*********@news-reader2.wanadoo.fr>, Cenekemoi
<tb***************@harrysoftware.ENVELERcom> wrote:

Bonjour à Mike <no****@please.com> qui nous a écrit :
Is there a way to check for the presence of a variable without giving
an error if not there? I don't want to define it on every page
unless I have to.

Use the typeof operator to check and see if your variable is defined.

example:

if (typeof(myVar) != 'undefined'){
//do processing
}

Better (IMHO) :

if (typeof(window['myVar') != 'undefined'){
//do processing
}

Thank both of you for your help but I couldn't do what I wanted to
anyway.

--
Dennis M. Marks
http://www.dcs-chico.com/~denmarks/
Replace domain.invalid with dcsi.net
-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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Jul 20 '05 #6

Thomas 'PointedEars' Lahn

Cenekemoi wrote:

if (typeof(window['myVar') != 'undefined'){ ^^^^^^^^^^^^^^^^ //do processing
}

Since "typeof" is an operator and not a method, the parantheses
are not required, (white)space suffices. Besides, there is a
nesting error in the code, it cannot work this way.
PointedEars

Jul 23 '05 #7

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