JavaScript Issue

[krismath]

Hi,
I wrote this function to check the validity of the text field,
StudentID if a radio button associated with it is clicked. The function
does not work...
function checkValidity(this) {

// Check the Radio buttons for which is checked.

var sid;
// it is group radio button and I am checking for the first one which
is associated with the text box of StudentID

for (var i=0;i <document.form1.searchby.length; i++)
{
if (document.form1.searchby[0].checked = true)
{

sid = document.form1.StudentID.value;

if (sid.length == 0)
{
alert("Student ID is Missing ");
return false;
}
}
}
}

[Randy Webb]

kr******@gmail.com said the following on 6/19/2006 1:38 PM:

Hi,
I wrote this function to check the validity of the text field,
StudentID if a radio button associated with it is clicked.
Use a checkbox. It will make your life simpler and if it's only purpose
is to tell whether a field should be used or not then a checkbox is more
appropriate.

The function does not work...
function checkValidity(this) {
Your parameter name is about the worst name you could choose. You don't
use it in your function but if you did then your function still wouldn't
work and wouldn't do what you think it would do.
// Check the Radio buttons for which is checked.
var sid;
// it is group radio button and I am checking for the first one which
is associated with the text box of StudentID

for (var i=0;i <document.form1.searchby.length; i++)
{
if (document.form1.searchby[0].checked = true)

<URL: http://www.jibbering.com/faq/faq_notes/form_access.html#faBut>

Explains how to get a reference to a Radio Button.

--
Randy
comp.lang.javascript FAQ - http://jibbering.com/faq & newsgroup weekly
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[Dr John Stockton]

JRS: In article <11**********************@f6g2000cwb.googlegroups. com>,
dated Mon, 19 Jun 2006 10:38:24 remote, seen in
news:comp.lang.javascript, kr******@gmail.com posted :

for (var i=0;i <document.form1.searchby.length; i++)
{
if (document.form1.searchby[0].checked = true)
That will assign true to document.form1.searchby[0].checked and the
following code will always be executed. You might have meant
searchby[i] too.
{

sid = document.form1.StudentID.value;

if (sid.length == 0)
{
alert("Student ID is Missing ");
return false;
}
}
}
}

AFAICS it is never necessary to use ==true or ==false, and doing so
indicates a fundamental lack of understanding.

Code in News articles, etc., should always by copy'n'pasted rather than
retyped.

--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.com/faq/>? JL/RC: FAQ of news:comp.lang.javascript
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.
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[John G Harris]

In article <FJ**************@merlyn.demon.co.uk>, Dr John Stockton
<jr*@merlyn.demon.co.uk> writes

<snip>

AFAICS it is never necessary to use ==true or ==false, and doing so
indicates a fundamental lack of understanding.

<snip>

It doesn't indicate a fundamental lack - it runs the risk of falling
foul of javascript's complicated rules for ==. For instance,

var x = 3;
if (x)
alert("True");
else
alert("False");

says 'true', whereas

var x = 3;
if (x == true)
alert("True");
else
alert("False");

says 'false'.

John
--
John Harris

[Dr John Stockton]

JRS: In article <3E**************@jgharris.demon.co.uk>, dated Wed, 21
Jun 2006 21:10:07 remote, seen in news:comp.lang.javascript, John G
Harris <jo**@nospam.demon.co.uk> posted :

In article <FJ**************@merlyn.demon.co.uk>, Dr John Stockton
<jr*@merlyn.demon.co.uk> writes

<snip>

AFAICS it is never necessary to use ==true or ==false, and doing so
indicates a fundamental lack of understanding.

<snip>

It doesn't indicate a fundamental lack - it runs the risk of falling
foul of javascript's complicated rules for ==. For instance,

It DOES indicate a fundamental lack - AND it runs the risk of falling
foul of javascript's complicated rules for ==.

--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.com/faq/>? JL/RC: FAQ of news:comp.lang.javascript
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demon.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

[Randy Webb]

Dr John Stockton said the following on 6/22/2006 6:55 AM:

JRS: In article <3E**************@jgharris.demon.co.uk>, dated Wed, 21
Jun 2006 21:10:07 remote, seen in news:comp.lang.javascript, John G
Harris <jo**@nospam.demon.co.uk> posted :

In article <FJ**************@merlyn.demon.co.uk>, Dr John Stockton
<jr*@merlyn.demon.co.uk> writes

<snip>

AFAICS it is never necessary to use ==true or ==false, and doing so
indicates a fundamental lack of understanding.

<snip>

It doesn't indicate a fundamental lack - it runs the risk of falling
foul of javascript's complicated rules for ==. For instance,

It DOES indicate a fundamental lack - AND it runs the risk of falling
foul of javascript's complicated rules for ==.

Adding ==true and ==false, to me, falls into the same category of
semicolons but the opposite. If you are not sure, use the ==true and
==false just to be sure. It's a "safer" approach, if there is one.

--
Randy
comp.lang.javascript FAQ - http://jibbering.com/faq & newsgroup weekly
Javascript Best Practices - http://www.JavascriptToolbox.com/bestpractices/

[Lasse Reichstein Nielsen]

Randy Webb <Hi************@aol.com> writes:

Adding ==true and ==false, to me, falls into the same category of
semicolons but the opposite. If you are not sure, use the ==true and
==false just to be sure. It's a "safer" approach, if there is one.

The problem is that it is not safer.

Try this:
---
var r = [];
for (var i = 0; i < 5; i++) {
if (i) { r.push(","); }
r.push(i);
}
alert(r.join("")); // yes I know there are simpler ways :)
---
Whoever wrote this knows the rules for converting numbers to booleans.
The result is alerting the string "0,1,2,3,4".

Now add someone who is less sure about it, and just to be "safer" he
adds "==true" to get "if (i == true) { ...".

The result now becomes "0,1234".
If you don't know for certain that the value in the condition is a
boolean, adding " == true" or " == false" is downright dangerous.

If you do know it, it's just not necessary.

/L
--
Lasse Reichstein Nielsen - lr*@hotpop.com
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleDOM.html>
'Faith without judgement merely degrades the spirit divine.'

[Jim Carlock]

"Lasse Reichstein Nielsen" <lr*@hotpop.com> wrote:

The problem is that it is not safer.

Try this: <--->
var r = [];
for (var i = 0; i < 5; i++) {
if (i) { r.push(","); }
r.push(i);
}
alert(r.join("")); // yes I know there are simpler ways :)
</---> Whoever wrote this knows the rules for converting numbers to
booleans. The result is alerting the string "0,1,2,3,4".

Now add someone who is less sure about it, and just to be
"safer" he adds "==true" to get "if (i == true) { ...".

The result now becomes "0,1234".

If you don't know for certain that the value in the condition is
a boolean, adding " == true" or " == false" is downright
dangerous.

If you do know it, it's just not necessary.

That can also be written as:

var r = [];
for (var i = 0; i < 5; i++) {
if (i != 0) { r.push(","); }
r.push(i);
}
alert(r.join("")); // yes I know there are simpler ways :)

which works upon the same principles as using ==. Right? After
all:

if (i)

literally translates to:

if (i != 0)

and not to:

if (i == 0)

If the suggestion involves deploying == when appropriate, that
leans towards the fact the end-user knows that when to deploy
== versus when to utilize !=, as in your example. ;-)

Nice try. Nice example. Thanks for passing it along.

--
Jim Carlock
Post replies to the group.

[Dr John Stockton]

JRS: In article <mu******************************@comcast.com>, dated
Thu, 22 Jun 2006 15:34:21 remote, seen in news:comp.lang.javascript,
Randy Webb <Hi************@aol.com> posted :

Dr John Stockton said the following on 6/22/2006 6:55 AM:

JRS: In article <3E**************@jgharris.demon.co.uk>, dated Wed, 21
Jun 2006 21:10:07 remote, seen in news:comp.lang.javascript, John G
Harris <jo**@nospam.demon.co.uk> posted :

In article <FJ**************@merlyn.demon.co.uk>, Dr John Stockton
<jr*@merlyn.demon.co.uk> writes

<snip>
AFAICS it is never necessary to use ==true or ==false, and doing so
indicates a fundamental lack of understanding.
<snip>

It doesn't indicate a fundamental lack - it runs the risk of falling
foul of javascript's complicated rules for ==. For instance,

It DOES indicate a fundamental lack - AND it runs the risk of falling
foul of javascript's complicated rules for ==.

Adding ==true and ==false, to me, falls into the same category of
semicolons but the opposite. If you are not sure, use the ==true and
==false just to be sure. It's a "safer" approach, if there is one.

Being unsure on the use of Boolean values clearly indicates a
fundamental lack of understanding - though alas not an uncommon one.

##

http://www.zdnetasia.com/techguide/w...9369022,00.htm
was evidently written by someone whose local time matched yours ...

Since it was advertised yesterday beside the display of this group in
Google, we may see ...

--
© John Stockton, Surrey, UK. ?@merlyn.demon.co.uk Turnpike v4.00 IE 4 ©
<URL:http://www.jibbering.com/faq/>? JL/RC: FAQ of news:comp.lang.javascript
<URL:http://www.merlyn.demon.co.uk/js-index.htm> jscr maths, dates, sources.
<URL:http://www.merlyn.demon.co.uk/> TP/BP/Delphi/jscr/&c, FAQ items, links.

[John G Harris]

In article <Wl**************@merlyn.demon.co.uk>, Dr John Stockton
<jr*@merlyn.demon.co.uk> writes

Thinking that this

<snip>

> AFAICS it is never necessary to use ==true or ==false, and doing so
> indicates a fundamental lack of understanding.

<snip>

is a consequence of this

<snip>Being unsure on the use of Boolean values clearly indicates a
fundamental lack of understanding - though
shows a fundamental lack of understanding of logic that is
alas not an uncommon one.

<snip>

John
--
John Harris