calling function with "return function()"

[Steve]

On page 392 of "Javascript the definitive guide" a function is called
like this:-

<form action="process form.cgi" onsubmit="retur n validateForm(); ">

Why, in this instance, is the return statement used in calling the
function validateForm rather than being included inside the function?

Thanks in advance,

[Joost Diepenmaat]

Re: calling function with &quot;return function()&quot ;

Steve <stephen.joung@ googlemail.comw rites:

On page 392 of "Javascript the definitive guide" a function is called
like this:-
>
<form action="process form.cgi" onsubmit="retur n validateForm(); ">
>
Why, in this instance, is the return statement used in calling the
function validateForm rather than being included inside the function?

Because onsubmit="retur n validateForm(); " is roughly equivalent to

element.onsubmi t = function() { return validateForm(); };

While, onsubmit="valid ateForm();" would be equivalent to

element.onsubmi t = function() { validateForm(); };

Also note that there is direct equivalent to element.submit = validateForm;


--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/

[Joost Diepenmaat]

Re: calling function with &quot;return function()&quot ;

Joost Diepenmaat <joost@zeekat.n lwrites:

Also note that there is direct equivalent to element.submit = validateForm;

^^^^^^^^^ I meant "...is NO direct..."

--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/

[Thomas 'PointedEars' Lahn]

Re: calling function with &quot;return function()&quot ;

Joost Diepenmaat wrote:

Joost Diepenmaat <joost@zeekat.n lwrites:

>Also note that there is direct equivalent to element.submit = validateForm;

^^^^^^^^^ I meant "...is NO direct..."

There is, but it makes no sense in the first place. If it worked, you would
be overwriting the form object's submit() method.


PointedEars
--
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
-- Richard Cornford, cljs, <f806at$ail$1$8 300dec7@news.de mon.co.uk>

[Steve]

Re: calling function with &quot;return function()&quot ;

On Jun 7, 8:11 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

Steve <stephen.jo...@ googlemail.comw rites:

On page 392 of "Javascript the definitive guide" a function is called
like this:-

>

<form action="process form.cgi" onsubmit="retur n validateForm(); ">

>

Why, in this instance, is the return statement used in calling the
function validateForm rather than being included inside the function?

>
Because onsubmit="retur n validateForm(); " is roughly equivalent to
>
element.onsubmi t = function() { return validateForm(); };
>
While, onsubmit="valid ateForm();" would be equivalent to
>
element.onsubmi t = function() { validateForm(); };
>

Thanks for the answer but I still don't get it. What would be the
difference in effect between calling

"element.onsubm it = function() { return validateForm(); };" and
calling

"element.onsubm it = function() { validateForm(); };" ?

Cheers.

[Joost Diepenmaat]

Re: calling function with &quot;return function()&quot ;

Steve <stephen.joung@ googlemail.comw rites:

Thanks for the answer but I still don't get it. What would be the
difference in effect between calling
>
"element.onsubm it = function() { return validateForm(); };" and
calling
>
"element.onsubm it = function() { validateForm(); };" ?

the second variant doesn't propagate the return value of
validateForm() to the form. you usually want to, because returning
false from an onsubmit handler will cancel the submit (while returning
nothing at all or true would cause the submit to continue). Not much
point in checking form fields and then just submitting it if it
doesn't validate.

--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/

[Steve]

Re: calling function with &quot;return function()&quot ;

On Jun 7, 9:22 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

Steve <stephen.jo...@ googlemail.comw rites:

Thanks for the answer but I still don't get it. What would be the
difference in effect between calling

>

"element.onsubm it = function() { return validateForm(); };" and
calling

>

"element.onsubm it = function() { validateForm(); };" ?

>
the second variant doesn't propagate the return value of
validateForm() to the form. you usually want to, because returning
false from an onsubmit handler will cancel the submit (while returning
nothing at all or true would cause the submit to continue). Not much
point in checking form fields and then just submitting it if it
doesn't validate.
>
--
Joost Diepenmaat | blog:http://joost.zeekat.nl/| work:http://zeekat.nl/

Yes but why not include the return statement inside the function, like
this:

function validateForm() {
if (document.forms[1].element[2]==null) {
return false;
}
else {
return true;
}
}

Cheers

[Joost Diepenmaat]

Re: calling function with &quot;return function()&quot ;

Steve <stephen.joung@ googlemail.comw rites:

On Jun 7, 9:22 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

>Steve <stephen.jo...@ googlemail.comw rites:

Thanks for the answer but I still don't get it. What would be the
difference in effect between calling

>>

"element.onsubm it = function() { return validateForm(); };" and
calling

>>

"element.onsubm it = function() { validateForm(); };" ?

>>
>the second variant doesn't propagate the return value of
>validateForm () to the form. you usually want to, because returning
>false from an onsubmit handler will cancel the submit (while returning
>nothing at all or true would cause the submit to continue). Not much
>point in checking form fields and then just submitting it if it
>doesn't validate.
>>

Yes but why not include the return statement inside the function, like
this:
>
function validateForm() {
if (document.forms[1].element[2]==null) {
return false;
}
else {
return true;
}
}
>

What I'm saying is you need the return statement(s) in the
validateForm function AND in the anonymous function.

--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/

[Tom de Neef]

Re: calling function with &quot;return function()&quot ;

"Steve" <stephen.joung@ googlemail.coms chreef in bericht
news:af923168-b93c-47c5-a8ed-19c8aa813ec8@s5 0g2000hsb.googl egroups.com...

On Jun 7, 9:22 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

>Steve <stephen.jo...@ googlemail.comw rites:

Thanks for the answer but I still don't get it. What would be the
difference in effect between calling

>>

"element.onsubm it = function() { return validateForm(); };" and
calling

>>

"element.onsubm it = function() { validateForm(); };" ?

>>
>the second variant doesn't propagate the return value of
>validateForm () to the form. you usually want to, because returning
>false from an onsubmit handler will cancel the submit (while returning
>nothing at all or true would cause the submit to continue). Not much
>point in checking form fields and then just submitting it if it
>doesn't validate.
>>
>--
>Joost Diepenmaat | blog:http://joost.zeekat.nl/| work:http://zeekat.nl/

>
Yes but why not include the return statement inside the function, like
this:
>
function validateForm() {
if (document.forms[1].element[2]==null) {
return false;
}
else {
return true;
}
}
>

Gentlemen experts, would it be correct to explain it in this way? :

Consider what you would have to code in the case there is no function but a
predefined value. For instance, you want to disable the submission of form
input.
You could have:
var submissionBlock = false;
element.onsubmi t = return submissionBlock ;
Meaning: pass the value of submissionBlock to the form. If you had
element.onsubmi t = submissionBlock
it would assign the value of submissionBlock to the property onsubmit of
element (which would not affect the form's excution).

Tom

[VK]

Re: calling function with &quot;return function()&quot ;

On Jun 7, 11:47 pm, Steve <stephen.jo...@ googlemail.comw rote:

On Jun 7, 9:22 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:
>
>
>

Steve <stephen.jo...@ googlemail.comw rites:

Thanks for the answer but I still don't get it. What would be the
difference in effect between calling

>

"element.onsubm it = function() { return validateForm(); };" and
calling

>

"element.onsubm it = function() { validateForm(); };" ?

>

the second variant doesn't propagate the return value of
validateForm() to the form. you usually want to, because returning
false from an onsubmit handler will cancel the submit (while returning
nothing at all or true would cause the submit to continue). Not much
point in checking form fields and then just submitting it if it
doesn't validate.

>

--
Joost Diepenmaat | blog:http://joost.zeekat.nl/|work:http://zeekat.nl/

>
Yes but why not include the return statement inside the function, like
this:
>
function validateForm() {
if (document.forms[1].element[2]==null) {
return false;
}
else {
return true;
}
>
}

You could check it yourself: in this case the form will be submitted
in either case _if_ validateForm is called from the intrinsic event
handler.

<form ... onsubmit="valid ateForm(this)">
is in fact internally
<form ... onsubmit= function anonymous() { validateForm(th is); }>

It means that no matter what validateForm returns, function anonymous
returns nothing (undefined) which is treated as a permission to submit
the form. It is an initial DOM 0 algorithm "oops" which is now
sustained by an ocean of existing scripts, so it is very hard (~=
impossible) to change it. Someone was thinking Perl I guess while
defining the procedure so he/she forgot that Javascript doesn't have
implicit return values for subroutines. The right algorithm would be
"if intrinsic onsubmit handler is set but returns nothing then treat
it as if it returns false". Too late to cry over it anyway. So the
regular algorithm fix is by using "piped return" like
<form ... onsubmit="retur n validateForm(th is)">

[Thomas 'PointedEars' Lahn]

Re: calling function with &quot;return function()&quot ;

Tom de Neef wrote:

"Steve" <stephen.joung@ googlemail.coms chreef [...]:

>On Jun 7, 9:22 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

>>Steve <stephen.jo...@ googlemail.comw rites:
>>>Thanks for the answer but I still don't get it. What would be the
>>>difference in effect between calling
>>>"element.ons ubmit = function() { return validateForm(); };" and
>>>calling
>>>"element.ons ubmit = function() { validateForm(); };" ?
>>the second variant doesn't propagate the return value of
>>validateForm( ) to the form. you usually want to, because returning
>>false from an onsubmit handler will cancel the submit (while returning
>>nothing at all or true would cause the submit to continue). Not much
>>point in checking form fields and then just submitting it if it
>>doesn't validate.

>Yes but why not include the return statement inside the function, like
>this:
>>
>function validateForm() {
> if (document.forms[1].element[2]==null) {
> return false;
> }
> else {
> return true;
> }
>}

>
Gentlemen experts, would it be correct to explain it in this way? :

Of course not.

Consider what you would have to code in the case there is no function but a
predefined value. For instance, you want to disable the submission of form
input.
You could have:
var submissionBlock = false;
element.onsubmi t = return submissionBlock ;
>
Meaning: pass the value of submissionBlock to the form.

This is a syntax error instead: `return' has been used outside of a function.

If you had
element.onsubmi t = submissionBlock
it would assign the value of submissionBlock to the property onsubmit of
element (which would not affect the form's excution).

Certainly not.


PointedEars
--
realism: HTML 4.01 Strict
evangelism: XHTML 1.0 Strict
madness: XHTML 1.1 as application/xhtml+xml
-- Bjoern Hoehrmann

[Steve]

Re: calling function with &quot;return function()&quot ;

On Jun 7, 9:59 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

>
What I'm saying is you need the return statement(s) in the
validateForm function AND in the anonymous function.
>

And what I am asking is why.

Cheers, Steve.

[Jorge]

Re: calling function with &quot;return function()&quot ;

On Jun 9, 11:16 am, Steve <stephen.jo...@ googlemail.comw rote:

On Jun 7, 9:59 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:
>

What I'm saying is you need the return statement(s) in the
validateForm function AND in the anonymous function.

>
And what I am asking is why.
>

Because (afaik... ) :

1.- element.onsubmi t= validateForm; --returns whatever
validateForm() returns.

2.- element.onsubmi t= "validateForm() "; is element.onsubmi t= function
() { validateForm() }; in disguise.

3.- element.onsubmi t= "return validateForm()" ; is element.onsubmi t=
function () { return validateForm() }; in disguise.

1 and 3 will return whatever validateForm() returns, but 2 will always
return undefined regardless :

<html><head><sc ript>
window.validate Form= function (e) { return "returned value" };
window.$= function (p) { return document.getEle mentById(p) };
window.onload= function () {

$('id1').onclic k= validateForm;
alert("1: "+($('id1')).on click);
alert("2: "+($('id2')).on click);
alert("3: "+($('id3')).on click);

};
</script></head><body>
<button id="id1">1</button>
<button id="id2" onclick= "validateForm() ">2</button>
<button id="id3" onclick= "return validateForm()" >3</button>
</body></html>

Not that this answers your question, though...

--Jorge.

[Joost Diepenmaat]

Re: calling function with &quot;return function()&quot ;

Steve <stephen.joung@ googlemail.comw rites:

On Jun 7, 9:59 pm, Joost Diepenmaat <jo...@zeekat.n lwrote:

>>
>What I'm saying is you need the return statement(s) in the
>validateForm function AND in the anonymous function.
>>

And what I am asking is why.

Because without a return statement there will be no returned
data. There really isn't much to explain; javascript REQUIRES a return
statement to return data.

Example:

function a() {
return "a";
}

function b() {
return a();
}

function c() {
a();
}


calls evaluating to

a() ="a"
b() ="a"
c() =undefined

--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/