"how to test for functions" should be in the FAQ, yes?

[Jake Barnes]

<FAQENTRY>

Weird. I go to Google and search for "javascript faq". These are the
top results:

http://www.javascripter.net/faq/index.htm
http://www.irt.org/script/script.htm
http://www.jibbering.com/faq/

I've got what I assume is an FAQ question:

"How can I check to see if a function has been defined?"
I searched on those pages for stuff like "define" and "function" and
"test" and didn't find my question.

[David Golightly]

On Sep 21, 4:20 pm, Jake Barnes <[e-mail]:

<FAQENTRY>

Weird. I go to Google and search for "javascript faq". These are the
top results:

http://www.javascripter.net/faq/inde...ering.com/faq/

I've got what I assume is an FAQ question:

"How can I check to see if a function has been defined?"

I searched on those pages for stuff like "define" and "function" and
"test" and didn't find my question.

To answer your question, "functions" aren't special in this case - you
need a general ability to test if an identifier is defined:

if (typeof possibleFn == 'function') {
// do stuff
}

gives you what you want; in general you can use

if (typeof possibleFn != 'undefined') {
// do stuff
}

for all your needs, unless you suspect possibleFn may be assigned a
non-function value somewhere, in which case the former (typeof
(possibleFn) == 'function') is what you want.

I don't know why the comp.lang.javascript FAQ is ranked 3rd in the
Google results. It's probably a matter of those other sites putting
greater importance on SEO.

Also, I doubt that this specific question will find its way into the
FAQ, unless under the guise of the general case (checking any
identifier's status); there are infinite questions that beginners ask,
and once they've read the FAQ, it's reasonable to come here to find
answers to stuff that's not there.

-David

[Richard Cornford]

David Golightly wrote:

On Sep 21, 4:20 pm, Jake Barnes wrote:

<snip>

>I've got what I assume is an FAQ question:

"How can I check to see if a function has been defined?"

<snip>

To answer your question, "functions" aren't special in
this case - you need a general ability to test if an
identifier is defined:

if (typeof possibleFn == 'function') {
// do stuff
}

gives you what you want; in general you can use

if (typeof possibleFn != 'undefined') {
// do stuff
}

<snip>

Also, I doubt that this specific question will find its way
into the FAQ, unless under the guise of the general case
(checking any identifier's status);

<snip>

And the general answer is already in the FAQ, in the resources linked to
from 4.26.

Richard.

[Jake Barnes]

On Sep 21, 9:15 pm, "Richard Cornford" <[e-mail]>
wrote:

David Golightly wrote:

On Sep 21, 4:20 pm, Jake Barnes wrote:

<snip>

I've got what I assume is an FAQ question:

"How can I check to see if a function has been defined?"

<snip>

To answer your question, "functions" aren't special in
this case - you need a general ability to test if an
identifier is defined:

if (typeof possibleFn == 'function') {
// do stuff
}

gives you what you want; in general you can use

if (typeof possibleFn != 'undefined') {
// do stuff
}

<snip>

Also, I doubt that this specific question will find its way
into the FAQ, unless under the guise of the general case
(checking any identifier's status);

<snip>

And the general answer is already in the FAQ, in the resources linked to
from 4.26.

Hmm, at jibbering, 4.26 is this:

4.26 How do I detect Opera/Netscape/IE?

http://www.jibbering.com/faq/#FAQ4_26
I don't see numbers for http://www.javascripter.net/faq/index.htm

At irt.org, 426 points at this:

http://www.irt.org/script/426.htm

Q426 How can I change the mouse pointer to an hourGlass prior to long
running scripts, then reset after the script complete?

So I don't see what you're suggesting. None of these 3 FAQs answer my
question, but I think my question, and the answer, should be in an
FAQ.

[Jake Barnes]

On Sep 21, 8:11 pm, David Golightly <[e-mail]:

On Sep 21, 4:20 pm, Jake Barnes <[e-mail]:

To answer your question, "functions" aren't special in this case - you
need a general ability to test if an identifier is defined:

if (typeof possibleFn == 'function') {
// do stuff

}

gives you what you want; in general you can use

if (typeof possibleFn != 'undefined') {
// do stuff

}

for all your needs, unless you suspect possibleFn may be assigned a
non-function value somewhere, in which case the former (typeof
(possibleFn) == 'function') is what you want.

I don't know why the comp.lang.javascript FAQ is ranked 3rd in the
Google results. It's probably a matter of those other sites putting
greater importance on SEO.

Also, I doubt that this specific question will find its way into the
FAQ, unless under the guise of the general case (checking any
identifier's status); there are infinite questions that beginners ask,
and once they've read the FAQ, it's reasonable to come here to find
answers to stuff that's not there.

You don't feel this question is asked frequently? I had the
impression it was in the category of "common".