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Hey Gang, I'm trying to figure out the best way to add two times together of
the format hh:mm:ss any suggestions would be great thanks Todd
Jul 23 '05 #1
15 7410
"Stormkid" <ba*****@goldengate.net> wrote in message
Hey Gang, I'm trying to figure out the best way to add two times together of the format hh:mm:ss any suggestions would be great thanks Todd

Convert all to seconds, add, then convert back. This way you can easily add
a third time later. For example:

var t1='12:34:56';
var t2='10:10:03';

t1=t1.split(/\D/);
t2=t2.split(/\D/);
var x1=parseInt(t1[0])*60*60 + parseInt(t1[1])*60 + parseInt(t1[2]);
var x2=parseInt(t2[0])*60*60 + parseInt(t2[1])*60 + parseInt(t2[2]);
var s=x1+x2;
var m=Math.floor(s/60); s=s%60;
var h=Math.floor(m/60); m=m%60;
var d=Math.floor(h/24); h=h%24;

You may wish to add leading zero's to numbers below 10 etc.
--Iv
Jul 23 '05 #2
Ivo wrote:
[snip]

Convert all to seconds, add, then convert back. This way you can easily add
a third time later. For example:

[snip]

Here is a modification of Ivo's example, I've created toSec(), toHr()
and toDay() functions. Of course there is no input validation and the
actual functions can probably be made more efficient.

You may still want to add leading zeros and include either toHr() or
toDay(), not both.

It is also more correct to use

this.form.elements['time1'].value

rather than the shorter but probably just as reliable:

this.form.time1.value
Cheers, Fred.

<script type="text/javascript">
function toSec(t) {
var b = t.split(/\D/);
return (+b[0])*60*60 + (+b[1])*60 + (+b[2]);
}

function toHr(s){
var m = Math.floor(s/60);
var h = Math.floor(m/60);
return h + ':' + m%60 + ':' + s%60;
}

function toDay(s){
var m = Math.floor(s/60);
var h = Math.floor(m/60);
var d = Math.floor(h/24);
return d + ':' + h%24 + ':' + m%60 + ':' + s%60;
}
</script>

<p>Enter times of format: hh:mm:ss</p>
<form name="fred" action="">
<input type="text" name="time1" cols="10">&nbsp;&nbsp;
<input type="text" name="time2" cols="10"><br>
+ toSec(this.form.time2.value))
+ '\nDays: ' + toDay(toSec(this.form.time1.value)
+ toSec(this.form.time2.value)));
">
</form>
Jul 23 '05 #3
Fred Oz wrote:

[snip]

[snip]
leading zero if the number passed has only one digit:

if (String(x).length < 2) x = '0' + x;
return x;
}
Use it like this in toHr()

Rob
Jul 23 '05 #4
The result would be undefined
Why would you want to add - say 11:55pm to 7:36am ?
I could see adding 2 hours and 45 minutes to a time, or something like that.

"Stormkid" <ba*****@goldengate.net> wrote in message
Hey Gang, I'm trying to figure out the best way to add two times together of the format hh:mm:ss any suggestions would be great thanks Todd

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Jul 23 '05 #5
dated Mon, 27 Sep 2004 14:17:40, seen in news:comp.lang.javascript,
Stormkid <ba*****@goldengate.net> posted :
Hey Gang, I'm trying to figure out the best way to add two times together of
the format hh:mm:ss any suggestions would be great thanks Todd

It makes no sense to add times, but it is perfectly OK to add durations.

The following illustrates what may be the shortest codes, for totals
less than 24 hours :-

D0 = "1970/1/3 " ; G = " GMT"
T1 = "11:22:33"
T2 = "01:55:44"

T3 = (new Date(+new Date(D0+T1+G) + +new Date(D0+T2+G))).toGMTString().m
atch(/\d\d:\d\d:\d\d/)

T3 = (new Date(+new Date(D0+T1+G) + +new Date(D0+T2+G))).toGMTString().s
ubstr(16, 8)

The second makes more assumptions. Both are slightly tested.
The method of Iv (Ivo) fails if any field is 08 or 09 (FAQ 4.12). Using
parseInt() serves no purpose for hh & mm, and a unary + is enough for
ss.

Fred's looks OK apart from leading zeroes; I think that it has two
superfluous (+ ) .

Rob's usable leading zero function has the defects that it sometimes
returns a string & sometimes a number, and that if it returns a number
the number-to-string conversion will be repeated. Consider
if ((x=String(x)).length < 2) x = '0' + x;

<FAQENTRY> Optimal LZ function needed!

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Jul 23 '05 #6
Dr John Stockton wrote:
<...>
and that if it returns a number
the number-to-string conversion will be repeated. Consider
if ((x=String(x)).length < 2) x = '0' + x;

<FAQENTRY> Optimal LZ function needed!

Optimal is always desirable, but it seems that there is often no
single optimally efficient computation, and/or optimally expressed
computation, because of the variations in the ways in which JS engines
peform in different browsers. Whether, for example, a type conversion
is carried out more than once may be less important regarding
computational efficiency than the actual expression used to manifest
the result.

In this given case, differences in performance will likely occur based
on whether the input value is provided as a string or as an integer.
A couple of alternatives to your suggestion above, always returning a
string, are:

x = "" + (-(x > 9) && "") + +x;

and

x = x < 10 ? "0" + +x : "" +x;

with the former being somewhat oblique, but reasonably efficient (and
just slightly different in the treatment of extraneous leading zeros
in the input string), while the latter is expressed more clearly, and
is more efficient with string input. The latter, without saying it is
the best that can be done, should also provide better balance of
efficient computation across browsers and input type.

../rh
Jul 23 '05 #7
dated Tue, 28 Sep 2004 19:24:33, seen in news:comp.lang.javascript, rh
<co********@yahoo.ca> posted :
Dr John Stockton wrote:
<...>
and that if it returns a number
the number-to-string conversion will be repeated. Consider
if ((x=String(x)).length < 2) x = '0' + x;

<FAQENTRY> Optimal LZ function needed!
Optimal is always desirable, but it seems that there is often no
single optimally efficient computation, and/or optimally expressed
computation, because of the variations in the ways in which JS engines
peform in different browsers. Whether, for example, a type conversion
is carried out more than once may be less important regarding
computational efficiency than the actual expression used to manifest
the result.

In this given case, differences in performance will likely occur based
on whether the input value is provided as a string or as an integer.

In the overwhelming majority of cases, the programmer will know whether
the input is a string or an integer.

The Leading Zero function is essentially a function for integer input.
If such string padding is wanted, it can either be done using a general
inefficient use of an integer function.

Rob's, omitting String( ) , is presumably optimum for strings.

One important question is whether it is *certain* that the number input
will be an integer in 0..99. If it is *certain* - which is the case for
getHours, etc. - then more methods become available, such as adding 100,
converting to string, and taking the last two characters (which is the
fastest way I know in MSIE4 VBscript). Otherwise, I would choose to
preserve the numerical value at the expense of format.
A couple of alternatives to your suggestion above, always returning a
string, are:

x = "" + (-(x > 9) && "") + +x;

and

x = x < 10 ? "0" + +x : "" +x;

with the former being somewhat oblique, but reasonably efficient (and
just slightly different in the treatment of extraneous leading zeros
in the input string), while the latter is expressed more clearly, and
is more efficient with string input. The latter, without saying it is
the best that can be done, should also provide better balance of
efficient computation across browsers and input type.

The second + seems unnecessary in the latter.

For non-negative integers,
'0'.substring(X>=10)+X // short but slow?
'0'.substr(X>=10)+X // shorter but slow?
I use
function LZ(x) { return (x<0||x>=10?"":"0") + x }
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Jul 23 '05 #8
Dr John Stockton wrote:
<co********@yahoo.ca> posted :
Dr John Stockton wrote:
<...>
and that if it returns a number
the number-to-string conversion will be repeated. Consider
if ((x=String(x)).length < 2) x = '0' + x;

<FAQENTRY> Optimal LZ function needed!
Optimal is always desirable, but it seems that there is often no
single optimally efficient computation, and/or optimally expressed
computation, because of the variations in the ways in which JS engines
peform in different browsers. Whether, for example, a type conversion
is carried out more than once may be less important regarding
computational efficiency than the actual expression used to manifest
the result.

In this given case, differences in performance will likely occur based
on whether the input value is provided as a string or as an integer.

In the overwhelming majority of cases, the programmer will know whether
the input is a string or an integer.

Possibly. But perhaps in a typeless language, in the overwhelming
majority of cases, it shouldn't be necessary for the programmer to
differentiate between the two. If it is, then it seems most sensible
to present the utility a prototype of the core object (not that you've
suggested anything to the contrary).
The Leading Zero function is essentially a function for integer input.
If such string padding is wanted, it can either be done using a general
inefficient use of an integer function.

Rob's, omitting String( ) , is presumably optimum for strings.
Somewhat surprisingly, it appears not to be. And that's what I meant
when saying "optimal" is hard to achieve as it depends on which JS
engine is performing the computation. Outside IE, computation
efficiency of that expression in several of the more popular browsers
(even with String() omitted) ranges in my tests from slow to dismal.

The point is that it is non-trivial to assess computational efficiency
by simply looking at the operations in an expression.

One important question is whether it is *certain* that the number input
will be an integer in 0..99. If it is *certain* - which is the case for
getHours, etc. - then more methods become available, such as adding 100,
converting to string, and taking the last two characters (which is the
fastest way I know in MSIE4 VBscript). Otherwise, I would choose to
preserve the numerical value at the expense of format.
A couple of alternatives to your suggestion above, always returning a
string, are:

x = "" + (-(x > 9) && "") + +x;

and

x = x < 10 ? "0" + +x : "" +x;
<...>
The second + seems unnecessary in the latter.
It's there to allow for a string with extraneous leading zeros, e.g.,
input of "09", which would be returned as "009" otherwise.

For non-negative integers,
'0'.substring(X>=10)+X // short but slow?
'0'.substr(X>=10)+X // shorter but slow?
Also, perhaps:

["0",""][+(x>=10)]+x; // short but (surprisingly) slow
I use
function LZ(x) { return (x<0||x>=10?"":"0") + x }

Which is good, probably optimal -- to be improved only by making it a
prototype :).

../rh
Jul 23 '05 #9
rh wrote:
x = x < 10 ? "0" + +x : "" +x;

<...>

The second + seems unnecessary in the latter.

It's there to allow for a string with extraneous leading zeros, e.g.,
input of "09", which would be returned as "009" otherwise.
I use
function LZ(x) { return (x<0||x>=10?"":"0") + x }

Which is good, probably optimal -- to be improved only by making it a
prototype :).

But allows for a string with extraneous leading zeros:

function LZ(x) { return (x<0||x>=10?"":"0") + x }

This could be corrected with:

function LZ(x) { return (x<0||x>=10?"":"0") + +x }

Alternatively:

String.prototype.LZ = function() { return (+this).LZ(); }
Number.prototype.LZ = function() { return (this < 0 || this >= 10 ? "" : "0")
+ this; }

--
Grant Wagner <gw*****@agricoreunited.com>
comp.lang.javascript FAQ - http://jibbering.com/faq

Jul 23 '05 #10
dated Wed, 29 Sep 2004 19:34:50, seen in news:comp.lang.javascript, rh
<co********@yahoo.ca> posted :
But perhaps in a typeless language, in the overwhelming
majority of cases, it shouldn't be necessary for the programmer to
differentiate between the two.
It is trivial, efficient, and not necessary.
If it is, then it seems most sensible
to present the utility a prototype of the core object (not that you've
suggested anything to the contrary).
To suit all cases, ISTM that it would need to be added to String and
Number. It's briefer to use LZ(D.getDate()) than D.getDate().LZ(), too!

The Leading Zero function is essentially a function for integer input.
If such string padding is wanted, it can either be done using a general
inefficient use of an integer function.

Rob's, omitting String( ) , is presumably optimum for strings.

Somewhat surprisingly, it appears not to be.

It would become
function addZero(x) { if (x.length < 2) x = '0' + x ; return x }

function addZero(x) { return x.length < 2 ? '0' + x : x }

is perhaps better, though.
And that's what I meant
when saying "optimal" is hard to achieve as it depends on which JS
engine is performing the computation. Outside IE, computation
efficiency of that expression in several of the more popular browsers
(even with String() omitted) ranges in my tests from slow to dismal.
In comparison with ???
The point is that it is non-trivial to assess computational efficiency
by simply looking at the operations in an expression.

Indeed. The easiest way is to post it here, claim it as good, and wait
for results.

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Jul 23 '05 #11
JRS: In article <41***************@agricoreunited.com>, dated Thu, 30
Sep 2004 16:01:28, seen in news:comp.lang.javascript, Grant Wagner
<gw*****@agricoreunited.com> posted :
rh wrote:

JRS wrote :
> I use
> function LZ(x) { return (x<0||x>=10?"":"0") + x }

Which is good, probably optimal -- to be improved only by making it a
prototype :).

But allows for a string with extraneous leading zeros:

function LZ(x) { return (x<0||x>=10?"":"0") + x }

As I said : the programmer knows what the parameter will be like. My LZ
is for use on Numbers, not on strings. '09' is not a Number, it is a
String.

In the rare (not happened yet) case that the item to be processed by LZ
is or might be a string, I'd use LX(+x).

To stretch a string, I would use something like
function Prfx(Q, L, c) { var s = Q+"" // ??
// if (!c) var c = ' '
if (c.length>0) while (s.length<L) { s = c+s } ;
return s }

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Jul 23 '05 #12
Grant Wagner wrote:
rh wrote:
> x = x < 10 ? "0" + +x : "" +x;
<...>
But allows for a string with extraneous leading zeros:

Actually, as intended though. It was a dubious attempt to match the
behaviour string input to an expression given by JRS -- in which it
turns out, he had no intention of allowing strings as input. So, time
to chuckle, perhaps, and move on.

However, I think I may ask for the criteria next time, including what
is meant by "optimal" ;-)

../rh
Jul 23 '05 #13
Dr John Stockton wrote:
dated Wed, 29 Sep 2004 19:34:50, seen in news:comp.lang.javascript, rh
<co********@yahoo.ca> posted :
But perhaps in a typeless language, in the overwhelming
majority of cases, it shouldn't be necessary for the programmer to
differentiate between the two.
It is trivial, efficient, and not necessary.
If it is, then it seems most sensible
to present the utility a prototype of the core object (not that you've
suggested anything to the contrary).

To suit all cases, ISTM that it would need to be added to String and
Number. It's briefer to use LZ(D.getDate()) than D.getDate().LZ(), too!

LZ is simply a case in point.

To me, it's much more a matter of an attempt to match the language,
because in providing recommended service utilities you're really
extending the language beyond what is provided in the base.

So, the two choices I see are tightly couple to a type through
prototype, or write a function that isn't tied to a type and provides
reasonable output based on "reasonable" input.

After all, it's this sort of flexibility in the language that allows
you to write such things as you have, e.g.:

'0'.substring(X>=10)

where the substring parameter is a logical value, yet you get a
well-defined and reasonable result (through implicit coercion to the
type the method actually understands). The same could be done with LZ,
with little or no cost in efficiency, when called with an integer
type.

Even if the decision is to prototype, the function could be made
common to the types that it supports.

<...>
Somewhat surprisingly, it appears not to be.

It would become
function addZero(x) { if (x.length < 2) x = '0' + x ; return x }

function addZero(x) { return x.length < 2 ? '0' + x : x }

is perhaps better, though.
And that's what I meant
when saying "optimal" is hard to achieve as it depends on which JS
engine is performing the computation. Outside IE, computation
efficiency of that expression in several of the more popular browsers
(even with String() omitted) ranges in my tests from slow to dismal.

In comparison with ???

A number of others given in the earlier posts.
The point is that it is non-trivial to assess computational efficiency
by simply looking at the operations in an expression.

Indeed. The easiest way is to post it here, claim it as good, and wait
for results.

Ah, yes, see who takes the bait! ;-)

../rh
Jul 23 '05 #14
dated Thu, 30 Sep 2004 16:35:08, seen in news:comp.lang.javascript, rh
<co********@yahoo.ca> posted :

However, I think I may ask for the criteria next time, including what
is meant by "optimal" ;-)

As a practical definition, any member of the set of solutions that
cannot be shown to be non-optimal, "cannot" being judged by "has not".

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Jul 23 '05 #15
Dr John Stockton wrote:
dated Thu, 30 Sep 2004 16:35:08, seen in news:comp.lang.javascript, rh
<co********@yahoo.ca> posted :

However, I think I may ask for the criteria next time, including what
is meant by "optimal" ;-)

As a practical definition, any member of the set of solutions that
cannot be shown to be non-optimal, "cannot" being judged by "has not".

I'm onto your game -- you'd like to see me blow my (recursive) stack!
Didn't work. :)

../rh
Jul 23 '05 #16