Date problem

**Ivo** · Jul 23 '05, 02:25 PM

Re: Date problem

"rhino" wrote[color=blue]
> This worked before October now it does not work. I think I know where the
> trouble is but I don't know how to fix it.
>
> if( ( d.getMonth()+1 ) < 10 ) { str = '0'; }
>
> str = str + ( d.getMonth()+1 ) + '/' + d.getDate() + '/';[/color]

str is now undefined since the 'if' is false and the engine never sees the
script block between the { and }. You should define the variable before
using it, and all will be well again...
Put the following line just before the above two to define your variable:

var str='';

(Those are two single quotes representing an empty string. You may also use
double quotes.)

Another solution would be to change the line with the 'if' block into this:

var str = d.getMonth() < 9 ? '0' : '';

HTH
--
Ivo

**Richard Cornford** · Jul 23 '05, 02:25 PM

Re: Date problem

rhino wrote:[color=blue]
> This worked before October now it does not work. I think
> I know where the trouble is but I don't know how to fix it.[/color]

The suspicion when October coincides with the manifestation of a problem
would usually be that the change to/form summer time/daylight saving
time is the cause. In this case I don't see that as significant.

As usual this question is asked without any indication of what
constituted "worked" when it did, and what symptoms represent not
working. There is also clearly an intended interaction with HTML
(named/IDed A elements probably) which have not been provided. Also
there is no indication of how, where and when the code is called. Thus a
question asked without context is unlikely to receive an answer that
represents a solution (except by coincidence).
[color=blue]
> function findVerse()
> {
> var d = new Date();
> var str;[/color]

The value of the local - str - variable is not defaulted so its value
will be undefined.
[color=blue]
> if( ( d.getMonth()+1 ) < 10 ) { str = '0'; }[/color]

Taking today's date (4th October 2004), - d.getMonth() - returns 9, add
one is 10, which is not less than 10 so the contents of the block
statement are not executed.

During months before October (in the same year) the contents of the
block statement would have been executed and a string value assigned
to - str -.
[color=blue]
> str = str + ( d.getMonth()+1 ) + '/' + d.getDate() + '/';[/color]

At this point, on this day, the Date object function calls result in the
numbers 9 and 4. Giving the expression:-

str = str + (9+1) + '/' + 4 + '/';
-or:-
str = str + 10 + '/' + 4 + '/';

The types involved being:-

str = undefined + number + string + number + string;

The addition/concatenation operator is resolved left to right so the
first expression evaluated is - (undefined + 10) -. Neither operand is a
string so the + operator performs numeric addition, type converting its
undefined operand into the numeric value NaN for the operation. NaN + 10
== NaN so the result is NaN.

The next operation becomes - (NaN + '/'), where one of the operands is a
string and so the numeric operand is type-converted into the string
"NaN", and "/" concatenated. Producing "NaN/". Form here on all
subsequent + operations have at least one string operand and so are
concatenation operations. Resulting in the string - "NaN/4/", which is
extremely unlikely to be the desired result.

So you got lucky and probably have a solution, though don't let that
encourage you to omit the context if you ask other questions here. The
quick solutions are:-

Default the initial value of the local variable - str - to an empty
string (forcing all + operations to be concatenation and avoiding an
initial - undefined - value of - str):-

var str = '';

- or provide an - else - branch for when getMonth is 9 or greater:-

if( ( d.getMonth()+1 ) < 10 ) {
str = '0';
}else{
str = '';
}

In the longer term the solution to this type of problem is not to employ
individuals to write javascript that do not understand javascript
(and/or are unwilling/unable to perform adequate testing. That is; if
someone writes a date based string outputting function the minimum they
should realistically be expected to do when testing is feed it a range
of dates spread across an appropriate interval (a year in this case) and
see that it does output the expected results.) (designers != programmers
(often)).

<snip>[color=blue]
> location.href = document.URL + '#' + str;[/color]
<snip>

It would probably be better not to be involving - document.URL - in this
operation. The - location.href - property being set already contains the
URL of the current page and the more object model properties used
without verification of the browser's support for them the more the
chances of enco9untering a browser that does not support one of them (or
supports it in an unusual way). Sticking with - location.href - only
removed the browser's support for - document.URL - form consideration.

I am also suspicious of the slashes in the constructed string, they may
need URL encoding prior to assignment.

Most modern browsers react appropriately to the assignment of fragment
identifier values directly to the - location.hash - property.

Richard.

**rhino** · Jul 23 '05, 02:25 PM

Re: Date problem

Now my code looks like this;

function findVerse()
{
var d = new Date();
var str;

str = ( d.getMonth()+1 ) + '/' + d.getDate() + '/';

if( d.getHours() >= 12 ) { str += 'PM'; }
else { str += 'AM'; }

location.href = document.URL + '#' + str;
return true;
}

Now it works. I also changed all the necessary name anchors from
<a name="01/01/AM"></a> ... <a name="12/09/AM"></a>
<a name="01/01/PM"></a> ... <a name="12/09/PM"></a>

to

<a name="1/1/AM"></a> ... <a name="12/9/AM"></a>
<a name="1/1/PM"></a> ... <a name="12/9/PM"></a>

in the page that is using this script. This script is in an external
Javascript document called by a link in the header of the HTML page. This
script <script>findVer se();</script> is at the bottom of the HTML page.

What the script is doing is creating the string 10/4/AM or 10/4/PM and
then finding the name anchor that matches and then displaying the correct
paragraph at the top of the page in a HTML document.

All is well again.

The other thing I thought about doing was putting the if statement back
in for

if( (d.getMonth()+1 ) < 10 ) { str = '0'; }

I would also need to have an if statement for

if( d.getDate() < 10 ) { str = '0' }

then I would need to know how to write the conditional statement for
these four string conditions and only one would be valid at a time
determined by the date, which would also determine the condition of the if
statements. I understand what I want the script to do. I don't
understand the rules or the syntax.

str = ( d.getMonth()+1 ) + '/' + d.getDate() + '/';

or

str = str + ( d.getMonth()+1 ) + '/' + d.getDate() + '/';

or

str = ( d.getMonth()+1 ) + '/' + str + d.getDate() + '/';

or

str = str + ( d.getMonth()+1 ) + '/' + str + d.getDate() + '/';

If some one feels like enlightening me on how to write the script to use
the correct string based on the date and the if statements for month and
date, I would be grateful.

Richard Cornford pointed out something about the location.href =
document.URL portion of the script. How would this be written without
using document.URL ?

Any information again will be gratefully appreciated,

Thanks,
Rhino

**Richard Cornford** · Jul 23 '05, 02:25 PM

Re: Date problem

rhino wrote:
<snip>[color=blue]
> Richard Cornford pointed out something about the
> location.href = document.URL portion of the script.
> How would this be written without using document.URL ?[/color]

location.href = location.href + '#' + str;

-or:-

location.href += '#' + str;

-or:-

location = location.href + '#' + str;

-or:-

location.hash = '#' + str; //though Opera <=6 doesn't like that one.

Richard.

**Dr John Stockton** · Jul 23 '05, 02:25 PM

Re: Date problem

JRS: In article <pan.2004.10.04 .13.11.22.40074 4@localhost.com >, dated
Mon, 4 Oct 2004 09:11:45, seen in news:comp.lang. javascript, rhino
<rhino@localhos t.com> posted :
[color=blue]
>This worked before October now it does not work. I think I know where the
>trouble is but I don't know how to fix it.[/color]
[color=blue]
> if( ( d.getMonth()+1 ) < 10 ) { str = '0'; }
>
> str = str + ( d.getMonth()+1 ) + '/' + d.getDate() + '/';[/color]

The operation of converting a Number to a two-digit string is common;
therefore, you should seek a function or method to do it. If you had
looked at recent posts in the group, you should have found a suggestion
that such should be in the newsgroup FAQ, and suggested code. And, if
you had used the newsgroup FAQ carefully, you would have found a link
for dates, including string formatting, including leading zeroes.

Your code is specific to Month, and fails.

You should have something like

str = LZ( d.getMonth()+1 ) + '/' + LZ( d.getDate() ) + '/' ;

<FAQENTRY> Change date3 to date2

Always, modularise out common or repeated functions, and test them
independently.

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

**rhino** · Jul 23 '05, 02:26 PM

Re: Date problem

My code is now working and I believe it will work on any month on any
day of the month.

Can any body see anything wrong with this code or is there a better,
cleaner, more appropriate way to this?

I am a newbie at writing Javascript.

This is at the top of the page that it is manipulating inside the body tag

/* The purpose of this code is to 1st get the current date and the time of
day as in is it AM or PM. Then the correct string needs to be found to
create the string in this format 01/01/AM or 12/31/PM. The leading zeros
are needed to work correctly with some browsers. Then the script applies
the string to match a name anchor in the document so the current date's AM
or PM paragraph appears.*/

function findVerse() {
var d = new Date();
var str='';
var str1='';
var str2='';

// the if statement is true in months 1-9
// the else statement is true in months 10-12
if( ( d.getMonth()+1 ) < 10 ) {
str1 = '0';
} else { str1 = '';}

// the if statement is true the 1st-9th of the month
// the else statement is true the 10th-end of the month
if( d.getDate() < 10 ) {
str2 = '0';
} else { str2 = ''; }

str = str1 + (d.getMonth()+1 ) + '/' + str2 + d.getDate() + '/';

if( d.getHours() >= 12 ) {
str += 'PM';
}
else {
str += 'AM';
}

location.href += '#' + str;

return true;
}

this is at the bottom of the same page inside the body tag

<script>findVer se();</script>

Thanks for any replies,

Rhino

**rhino** · Jul 23 '05, 02:26 PM

Re: Date problem

On Mon, 04 Oct 2004 20:57:14 +0100, Dr John Stockton wrote:
[color=blue]
> The operation of converting a Number to a two-digit string is common;
> therefore, you should seek a function or method to do it. If you had
> looked at recent posts in the group, you should have found a suggestion
> that such should be in the newsgroup FAQ, and suggested code. And, if
> you had used the newsgroup FAQ carefully, you would have found a link
> for dates, including string formatting, including leading zeroes.
>
> Your code is specific to Month, and fails.
>
> You should have something like
>
> str = LZ( d.getMonth()+1 ) + '/' + LZ( d.getDate() ) + '/' ;
>
> <FAQENTRY> Change date3 to date2
>
> Always, modularise out common or repeated functions, and test them
> independently.[/color]

I found a list of FAQs but I did not find what you were talking about.

**Michael Winter** · Jul 23 '05, 02:26 PM

Re: Date problem

On Mon, 04 Oct 2004 22:52:17 -0400, rhino <rhino@localhos t.com> wrote:

[snip]
[color=blue]
> Can any body see anything wrong with this code or is there a better,
> cleaner, more appropriate way to this?[/color]

Yes. As Dr Stockton suggested, a function can be used to pad the number:

function lz(n) {return ((n < 10) ? '0' : '') + n;}

which reduces code duplication.

[snip]

function findVerse() {
var d = new Date();

location.href += '#' + lz(d.getMonth() + 1)
+ '/' + lz(d.getDate())
+ '/' + ((12 > d.getHours()) ? 'AM' : 'PM');
}

You could probably improve the speed of this code by using an array to
hold the different parts of the string and concatenate them with the
Array.prototype .join method, but it's not really worth it in this case.
[color=blue]
> function findVerse() {
> var d = new Date();
> var str='';
> var str1='';
> var str2='';[/color]

Whilst there's no harm in doing them, these initialisations are pointless.
In the code below, all code paths result in a string value being assigned
to each variable.
[color=blue]
> // the if statement is true in months 1-9
> // the else statement is true in months 10-12
> if( ( d.getMonth()+1 ) < 10 ) {
> str1 = '0';
> } else { str1 = '';}
>
> // the if statement is true the 1st-9th of the month
> // the else statement is true the 10th-end of the month
> if( d.getDate() < 10 ) {
> str2 = '0';
> } else { str2 = ''; }
>
> str = str1 + (d.getMonth()+1 ) + '/' + str2 + d.getDate() + '/';[/color]

It would have been better to retrieve and save the values of (d.getMonth()
+ 1) and d.getDate() once, rather than calling the functions twice.

[snip]
[color=blue]
> return true;[/color]

This return statement isn't needed as it does nothing useful.
[color=blue]
> this is at the bottom of the same page inside the body tag
>
> <script>findVer se();</script>[/color]

Why not call the function when the load event fires, seeing as you intend
to run the code once the page has loaded.

<body ... onload="findVer se();">

Mike

--
Michael Winter
Replace ".invalid" with ".uk" to reply by e-mail.

**Andrew Thompson** · Jul 23 '05, 02:26 PM

Re: Date problem

On Mon, 04 Oct 2004 23:10:14 -0400, rhino wrote:

(Dr. J. S.)[color=blue][color=green]
>> <FAQENTRY>[/color][/color]
....[color=blue]
> I found a list of FAQs but I did not find what you were talking about.[/color]

Are you referring to <FAQENTRY>?

It is a signal by the poster that they feel the question is so
frequently asked that the answer *should* be included in the FAQ.

--
Andrew Thompson
http://www.PhySci.org/codes/ Web & IT Help
http://www.PhySci.org/ Open-source software suite
http://www.1point1C.org/ Science & Technology
http://www.lensescapes.com/ Images that escape the mundane

**Randy Webb** · Jul 23 '05, 02:26 PM

Re: Date problem

Andrew Thompson wrote:
[color=blue]
> On Mon, 04 Oct 2004 23:10:14 -0400, rhino wrote:
>
> (Dr. J. S.)
>[color=green][color=darkred]
>>><FAQENTRY>[/color][/color]
>
> ....
>[color=green]
>>I found a list of FAQs but I did not find what you were talking about.[/color]
>
>
> Are you referring to <FAQENTRY>?
>
> It is a signal by the poster that they feel the question is so
> frequently asked that the answer *should* be included in the FAQ.
>[/color]

The irony is that the fa*entry is explained in the FAQ :-x

--
Randy
comp.lang.javas cript FAQ - http://jibbering.com/faq

**Andrew Thompson** · Jul 23 '05, 02:26 PM

Re: Date problem

On Tue, 05 Oct 2004 05:57:17 -0400, Randy Webb wrote:

(A.T.)[color=blue][color=green]
>> Are you referring to <FA*ENTRY>?[/color][/color]
...[color=blue]
> The irony is that the fa*entry is explained in the FAQ :-x[/color]

ROTFLMAO. I knew I'd seen that *somewhere*. ;-)

--
Andrew Thompson
http://www.PhySci.org/codes/ Web & IT Help
http://www.PhySci.org/ Open-source software suite
http://www.1point1C.org/ Science & Technology
http://www.lensescapes.com/ Images that escape the mundane

**Evertjan.** · Jul 23 '05, 02:26 PM

Re: Date problem

Randy Webb wrote on 05 okt 2004 in comp.lang.javas cript:
[color=blue][color=green]
>> Are you referring to <FAQENTRY>?
>>
>> It is a signal by the poster that they feel the question is so
>> frequently asked that the answer *should* be included in the FAQ.
>>[/color]
>
> The irony is that the fa*entry is explained in the FAQ :-x[/color]

It is like a box,
with a note inside it,
saying:

"Look into this box!"

--
Evertjan.
The Netherlands.
(Please change the x'es to dots in my emailaddress,
but let us keep the discussions in the newsgroup)

**Richard Cornford** · Jul 23 '05, 02:26 PM

Re: Date problem

Evertjan. wrote:[color=blue]
> Randy Webb wrote:
>[color=green][color=darkred]
>>> Are you referring to <FA....RY>?
>>>
>>> It is a signal by the poster that they feel the question
>>> is so frequently asked that the answer *should* be included
>>> in the FAQ.[/color]
>>
>> The irony is that the fa*entry is explained in the FAQ :-x[/color]
>
> It is like a box,
> with a note inside it,
> saying:
>
> "Look into this box!"[/color]

It is not as if there aren't quite a lot of notes outside the box saying
"look in that box". Like the one in Dr John Stockton's signature
saying:-

<URL:http://www.jibbering.c om/faq/> JL/RC: FAQ of
news:comp.lang. javascript

Richard.

**Dr John Stockton** · Jul 23 '05, 02:27 PM

Re: Date problem

JRS: In article <pan.2004.10.05 .03.10.09.39343 9@localhost.com >, dated
Mon, 4 Oct 2004 23:10:14, seen in news:comp.lang. javascript, rhino
<rhino@localhos t.com> posted :[color=blue]
>On Mon, 04 Oct 2004 20:57:14 +0100, Dr John Stockton wrote:
>[color=green]
>> The operation of converting a Number to a two-digit string is common;
>> therefore, you should seek a function or method to do it. If you had
>> looked at recent posts in the group, you should have found a suggestion
>> that such should be in the newsgroup FAQ, and suggested code. And, if
>> you had used the newsgroup FAQ carefully, you would have found a link
>> for dates, including string formatting, including leading zeroes.
>>
>> Your code is specific to Month, and fails.
>>
>> You should have something like
>>
>> str = LZ( d.getMonth()+1 ) + '/' + LZ( d.getDate() ) + '/' ;
>>
>> <FAQENTRY> Change date3 to date2
>>
>> Always, modularise out common or repeated functions, and test them
>> independently.[/color]
>
>I found a list of FAQs but I did not find what you were talking about.[/color]

What was the URL of the list of FAQs that you found?

The newsgroup FAQ is posted to the group thrice weekly (bi-partly), and
was cited in my signature, line 2.

To find information on manipulating times, dates and the lastModified
date and time in javascript, just scan (Ctrl-F?) the FAQ for relevant
words; or consider signature line 3.

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

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