Javascript Switch

**Mike** · Jul 20 '05, 02:59 PM

Re: Javascript Switch

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

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

example:

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

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

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

**Cenekemoi** · Jul 20 '05, 02:59 PM

Re: Javascript Switch

Bonjour à Mike <nospam@please. com> qui nous a écrit :[color=blue][color=green]
>> 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.[/color]
>
> Use the typeof operator to check and see if your variable is defined.
>
> example:
>
> if (typeof(myVar) != 'undefined'){
> //do processing
> }[/color]

Better (IMHO) :

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

--
Cordialement, Thierry ;-)

**Michael Winter** · Jul 20 '05, 02:59 PM

Re: Javascript Switch

On Thu, 04 Mar 2004 07:09:47 -0800, Dennis M. Marks
<denmarks@domai n.invalid> wrote:

[snip]
[color=blue]
> 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.[/color]

function isDefined( ref ) {
return 'undefined' != typeof ref;
}
...
if( isDefined( aVariable )) {
...
}
[color=blue]
> BTW: If I have a script like this: <script src="xxx"
> type="text/javascript">som e code</script>. Will "some code" be
> processed before source code, after source code, or not at all. Is
> it consistant on all browsers?[/color]

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.Winter@blueyo nder.co.invalid (replace ".invalid" with ".uk" to reply)

**Randy Webb** · Jul 20 '05, 03:00 PM

Re: Javascript Switch

Dennis M. Marks wrote:[color=blue]
> 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.[/color]

Check window/document.locati on.href and the title won't matter.

[color=blue]
> 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">som e code</script>. Will "some code" be
> processed before source code, after source code, or not at all. Is it
> consistant on all browsers?[/color]

Not at all unless the browser doesn't understand the src attribute.

--
Randy
Chance Favors The Prepared Mind
comp.lang.javas cript FAQ - http://jibbering.com/faq/

**Dennis M. Marks** · Jul 20 '05, 03:00 PM

Re: Javascript Switch

In article <c27ipc$v3$1@ne ws-reader2.wanadoo .fr>, Cenekemoi
<tbaudessonENLE VER@harrysoftwa re.ENVELERcom> wrote:
[color=blue]
> Bonjour à Mike <nospam@please. com> qui nous a écrit :[color=green][color=darkred]
> >> 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.[/color]
> >
> > Use the typeof operator to check and see if your variable is defined.
> >
> > example:
> >
> > if (typeof(myVar) != 'undefined'){
> > //do processing
> > }[/color]
>
> Better (IMHO) :
>
> if (typeof(window['myVar') != 'undefined'){
> //do processing
> }[/color]
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

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**Thomas 'PointedEars' Lahn** · Jul 23 '05, 10:10 AM

Re: Javascript Switch

Cenekemoi wrote:
[color=blue]
> if (typeof(window['myVar') != 'undefined'){[/color]
^^^^^^^^^^^^^^^ ^[color=blue]
> //do processing
> }[/color]

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

Javascript Switch

Javascript Switch

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