Javascript and working with dates

[rhaazy]

I need to write some javascript that will return a date string in the
form mm/dd/yyyy.

The date needs to be today's date - 30 days.

Is there a relatively straight forward way to do this?

So far all I can find is a mess of variables for month, day, and year,
and combining some date functions together, etc etc. Seems like a lot
of work for what should be very simple.

[SAM]

Re: Javascript and working with dates

rhaazy a écrit :

I need to write some javascript that will return a date string in the
form mm/dd/yyyy.
>
The date needs to be today's date - 30 days.
>
Is there a relatively straight forward way to do this?

http://www.merlyn.demon.co.uk/js-date1.htm#incr

So far all I can find is a mess of variables for month, day, and year,
and combining some date functions together, etc etc. Seems like a lot
of work for what should be very simple.

and what do you think we have to do when we want the date in french ?
dd/mm/yyyy

var D = new Date();
D.setMonth(D.ge tMonth()-1)
alert( D.getDate()+'/'+(+D.getMonth( )+1)+'/'+D.getFullYear () );

--19/8/2008

--
sm

[rhaazy]

Re: Javascript and working with dates

On Sep 19, 3:04 pm, SAM <stephanemoriau x.NoAd...@wanad oo.fr.invalid>
wrote:

rhaazy a écrit :
>

I need to write some javascript that will return a date string in the
form mm/dd/yyyy.

>

The date needs to be today's date - 30 days.

>

Is there a relatively straight forward way to do this?

>

http://www.merlyn.demon.co.uk/js-date1.htm#incr

>

So far all I can find is a mess of variables for month, day, and year,
and combining some date functions together, etc etc.  Seems like a lot
of work for what should be very simple.

>
and what do you think we have to do when we want the date in french ?
  dd/mm/yyyy
>
var D = new Date();
D.setMonth(D.ge tMonth()-1)
alert( D.getDate()+'/'+(+D.getMonth( )+1)+'/'+D.getFullYear () );
>
  --19/8/2008
>
--
sm

Thats fine if all I want is a date, but to be able to subtract 30 days
from any given date introduces a huge mess of logic that needs to be
coded.
I decided to just find an open source date library that had decent
parsing functions for my purpose.

Thanks for the post.

[Joost Diepenmaat]

Re: Javascript and working with dates

rhaazy <rhaazy@gmail.c omwrites:

On Sep 19, 3:04 pm, SAM <stephanemoriau x.NoAd...@wanad oo.fr.invalid>
wrote:
Thats fine if all I want is a date, but to be able to subtract 30 days
from any given date introduces a huge mess of logic that needs to be
coded.

That's because dates - and times - are VERY messy. A library able to
manipulate dates that is complete enough to be /globally/ useful would
be very large. See for example the amount of stuff in the perl DateTime
project:

http://datetime.perl.org/?Modules

I decided to just find an open source date library that had decent
parsing functions for my purpose.

If you can find a decent library, that's probably the best way to handle
this problem.


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

[Stevo]

Re: Javascript and working with dates

rhaazy wrote:

On Sep 19, 3:04 pm, SAM <stephanemoriau x.NoAd...@wanad oo.fr.invalid>
wrote:

>var D = new Date();
>D.setMonth(D.g etMonth()-1)
>alert( D.getDate()+'/'+(+D.getMonth( )+1)+'/'+D.getFullYear () );
> --19/8/2008

Thats fine if all I want is a date, but to be able to subtract 30 days
from any given date introduces a huge mess of logic that needs to be
coded.

I can't recall any language that makes dealing with dates easy.

[Lasse Reichstein Nielsen]

Re: Javascript and working with dates

rhaazy <rhaazy@gmail.c omwrites:

I need to write some javascript that will return a date string in the
form mm/dd/yyyy.
>
The date needs to be today's date - 30 days.
>
Is there a relatively straight forward way to do this?

var date = new Date();
date.setDate(da te.getDate()-30);
var day = date.getDate();
var mth = date.getMonth() ;
var yr = date.getFullYea r();
var format = (day < 10 ? "0" : "") + day + "/" +
(mth < 10 ? "0" : "") + mth + "/" +
yr;

So far all I can find is a mess of variables for month, day, and year,
and combining some date functions together, etc etc. Seems like a lot
of work for what should be very simple.

There isn't a date formatter built in. For most cases, it's not worth
it anyway. Just make one function to format your dates as you want
it and use that wherever it's needed.

/L
--
Lasse Reichstein Nielsen
DHTML Death Colors: <URL:http://www.infimum.dk/HTML/rasterTriangleD OM.html>
'Faith without judgement merely degrades the spirit divine.'

[SAM]

Re: Javascript and working with dates

rhaazy a écrit :

On Sep 19, 3:04 pm, SAM <stephanemoriau x.NoAd...@wanad oo.fr.invalid>
wrote:

>rhaazy a écrit :
>>

>>I need to write some javascript that will return a date string in the
>>form mm/dd/yyyy.
>>The date needs to be today's date - 30 days.

>>
>var D = new Date();
>D.setMonth(D.g etMonth()-1)
>alert( D.getDate()+'/'+(+D.getMonth( )+1)+'/'+D.getFullYear () );
>>
> --19/8/2008

>
Thats fine if all I want is a date,

don't you want date ? ("mm/dd/yyyy" you did say)

but to be able to subtract 30 days

and *absoloutly* 30 days ?

from any given date introduces a huge mess of logic that needs to be
coded.

Example with a trap over February:
=============== =============== ====
var y = 2005, m = 03, d = 30; // 30/03/2005 (in dd/mm/yyyy)
var D = new Date(y, +m-1, d); // the orginal JS date
D.setDate(D.get Date()-30); // 30 days less
// that is done
alert( d+'/'+m+'/'+y+
' = original date\n'+
D.getDate()+'/'+(+D.getMonth( )+1)+'/'+D.getFullYear ()+
' = date - 30 days'):


--
sm

[SAM]

Re: Javascript and working with dates

Lasse Reichstein Nielsen a écrit :

rhaazy <rhaazy@gmail.c omwrites:

>>
>The date needs to be today's date - 30 days.
>>
>Is there a relatively straight forward way to do this?

>
var date = new Date();
date.setDate(da te.getDate()-30);
var day = date.getDate();
var mth = date.getMonth() ;

months begin by '0' in JS. No ?
so :
var mth = +date.getMonth( )+1;

var yr = date.getFullYea r();
var format = (day < 10 ? "0" : "") + day + "/" +
(mth < 10 ? "0" : "") + mth + "/" +
yr;

[Conrad Lender]

Re: Javascript and working with dates

On 2008-09-20 00:30, Lasse Reichstein Nielsen wrote:

There isn't a date formatter built in. For most cases, it's not worth
it anyway. Just make one function to format your dates as you want
it and use that wherever it's needed.

Here's one simple way to retro-fit a date formatting method. It
implements a subset of formats from strftime(3); the PHP function of the
same name is also similar. Some of the formats are missing, like the
names of months, week days, etc, because they were not required when the
method was written. Note: some of the formats are different from what
you might expect - read the comments and adjust the code as you see fit.


Usage:
var d = new Date(2008, 3, 4);
var dstr1 = d.fmt("%m/%d/%Y");
var dstr2 = d.fmt("%d.%m.%Y ");


/* a simple date formatting method */
Date.prototype. fmt = function (format) {
var buffer = "";
var chr, nxt;
for (var i = 0, len = format.length; i < len; ++i) {
chr = format.substr(i , 1);
if (chr != "%") {
buffer += chr;
continue;
}
nxt = format.substr(i + 1, 1);
if (nxt == "C") { // 2-digit century (eg "19" or "20")
buffer += String(Math.flo or( /* this should be one line */
this.getFullYea r() / 100)).padFront( "0", 2);
} else if (nxt == "d") { // day of month (01 to 31)
buffer += String(this.get Date()).padFron t("0", 2);
} else if (nxt == "F") { // month of year (1 to 12)
buffer += (this.getMonth( ) + 1);
} else if (nxt == "f") { // day of month (1 to 31)
buffer += this.getDate();
} else if (nxt == "H") { // 24h hours (00 - 23)
buffer += String(this.get Hours()).padFro nt("0", 2);
} else if (nxt == "M") { // minutes (00 - 59)
buffer += String(this.get Minutes()).padF ront("0", 2);
} else if (nxt == "m") { // month of year (01 to 12)
buffer += String(this.get Month() + 1).padFront("0" , 2);
} else if (nxt == "n") { // newline
buffer += "\n";
} else if (nxt == "R") { // 24h time (%H:%M)
buffer += String(this.get Hours()).padFro nt("0", 2)
+ ":"
+ String(this.get Minutes()).padF ront("0", 2);
} else if (nxt == "S") { // seconds (00 - 59)
buffer += String(this.get Seconds()).padF ront("0", 2);
} else if (nxt == "T") { // 24h time (%H:%M:%S)
buffer += String(this.get Hours()).padFro nt("0", 2)
+ ":"
+ String(this.get Minutes()).padF ront("0", 2)
+ ":"
+ String(this.get Seconds()).padF ront("0", 2);
} else if (nxt == "Y") { // 4-digit year
buffer += this.getFullYea r();
} else if (nxt == "y") { // 2-digit year
var y = String(this.get FullYear());
buffer += y.substr(y.leng th -2, 2);
} else if (nxt == "%") { // literal "%" character
buffer += "%";
} else {
buffer += format.substr(i , 2);
}
++i; // skip next
}
return buffer;
}


In this form, it also requires an extension to the String prototype object:

/* left-pads the string with {chr} until it is {len} characters long */
String.prototyp e.padFront = function (chr, len) {
if (this.length >= len) {
return this;
} else {
return chr.repeat(len - this.length) + this;
}
}

/* returns the string repeated {n} times */
String.prototyp e.repeat = function (n) {
if (n < 1) return "";
return (new Array(n + 1)).join(this);
}


If you don't like to mess with the native String and Date types, you
could refactor these methods as simple global methods (with date and
string arguments, respectively).


- Conrad

[sasuke]

Re: Javascript and working with dates

On Sep 20, 6:24 am, Conrad Lender <crlen...@yahoo .comwrote:

Usage:
    var d = new Date(2008, 3, 4);
    var dstr1 = d.fmt("%m/%d/%Y");
    var dstr2 = d.fmt("%d.%m.%Y ");
>
/* a simple date formatting method */
Date.prototype. fmt = function (format) {
    var buffer = "";
    var chr, nxt;
    for (var i = 0, len = format.length; i < len; ++i) {
        chr = format.substr(i , 1);
        if (chr != "%") {
            buffer += chr;
            continue;
        }
        nxt = format.substr(i + 1, 1);
        if (nxt == "C") {           // 2-digit century (eg "19" or "20")
            buffer += String(Math.flo or(   /* this shouldbe one line */
                this.getFullYea r() / 100)).padFront( "0", 2);
        } else if (nxt == "d") {    // day of month (01 to 31)
            buffer += String(this.get Date()).padFron t("0", 2);
        } else if (nxt == "F") {    // month of year (1 to 12)
            buffer += (this.getMonth( ) + 1);
        } else if (nxt == "f") {    // day of month (1 to31)
            buffer += this.getDate();
        } else if (nxt == "H") {    // 24h hours (00 - 23)
            buffer += String(this.get Hours()).padFro nt("0",2);
        } else if (nxt == "M") {    // minutes (00 - 59)
            buffer += String(this.get Minutes()).padF ront("0", 2);
        } else if (nxt == "m") {    // month of year (01 to 12)
            buffer += String(this.get Month() + 1).padFront("0" , 2);
        } else if (nxt == "n") {    // newline
            buffer += "\n";
        } else if (nxt == "R") {    // 24h time (%H:%M)
            buffer += String(this.get Hours()).padFro nt("0",2)
                    + ":"
                    + String(this.get Minutes()).padF ront("0", 2);
        } else if (nxt == "S") {    // seconds (00 - 59)
            buffer += String(this.get Seconds()).padF ront("0", 2);
        } else if (nxt == "T") {    // 24h time (%H:%M:%S)
            buffer += String(this.get Hours()).padFro nt("0",2)
                    + ":"
                    + String(this.get Minutes()).padF ront("0", 2)
                    + ":"
                    + String(this.get Seconds()).padF ront("0", 2);
        } else if (nxt == "Y") {    // 4-digit year
            buffer += this.getFullYea r();
        } else if (nxt == "y") {    // 2-digit year
            var y = String(this.get FullYear());
            buffer += y.substr(y.leng th -2, 2);
        } else if (nxt == "%") {    // literal "%" character
            buffer += "%";
        } else {
            buffer += format.substr(i , 2);
        }
        ++i; // skip next
    }
    return buffer;
>
}
>
In this form, it also requires an extension to the String prototype object:
>
/* left-pads the string with {chr} until it is {len} characters long */
String.prototyp e.padFront = function (chr, len) {
    if (this.length >= len) {
        return this;
    } else {
        return chr.repeat(len - this.length) + this;
    }
>
}
>
/* returns the string repeated {n} times */
String.prototyp e.repeat = function (n) {
    if (n < 1) return "";
    return (new Array(n + 1)).join(this);
>
}

Nice and compact implementation, 5 stars! A improvement here might be
using Array as buffer instead of String since Strings in Javascript
are immutable thereby preventing temporary string object creation.

/sasuke

[Thomas 'PointedEars' Lahn]

Re: Javascript and working with dates

sasuke wrote:

On Sep 20, 6:24 am, Conrad Lender <crlen...@yahoo .comwrote:

>Usage:
> var d = new Date(2008, 3, 4);
> var dstr1 = d.fmt("%m/%d/%Y");
> var dstr2 = d.fmt("%d.%m.%Y ");
>>
>/* a simple date formatting method */
>Date.prototype .fmt = function (format) {
> [50 lines of code]
>}
>>
>In this form, it also requires an extension to the String prototype object:
>>
>/* left-pads the string with {chr} until it is {len} characters long */
>String.prototy pe.padFront = function (chr, len) {
> if (this.length >= len) {
> return this;
> } else {
> return chr.repeat(len - this.length) + this;
> }
>>
>}
>>
>/* returns the string repeated {n} times */
>String.prototy pe.repeat = function (n) {
> if (n < 1) return "";
> return (new Array(n + 1)).join(this);
>>
>}

>
Nice and compact implementation, 5 stars!

Compact? Maybe String.prototyp e.padFront() and String.prototyp e.repeat().

A improvement here might be using Array as buffer instead of String

Or no user-defined buffer at all.

since Strings in Javascript are immutable thereby preventing temporary
string object creation.

Non sequitur.


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>

[Thomas 'PointedEars' Lahn]

Re: Javascript and working with dates

Conrad Lender wrote:

On 2008-09-20 00:30, Lasse Reichstein Nielsen wrote:

>There isn't a date formatter built in. For most cases, it's not worth
>it anyway. Just make one function to format your dates as you want
>it and use that wherever it's needed.

>
Here's one simple way to retro-fit a date formatting method. It
implements a subset of formats from strftime(3); the PHP function of the
same name is also similar. Some of the formats are missing, like the
names of months, week days, etc, because they were not required when the
method was written. Note: some of the formats are different from what
you might expect - read the comments and adjust the code as you see fit.

[x] done

Usage:
var d = new Date(2008, 3, 4);
var dstr1 = d.fmt("%m/%d/%Y");
var dstr2 = d.fmt("%d.%m.%Y ");
>
>
/* a simple date formatting method */
Date.prototype. fmt = function (format) {
var buffer = "";
var chr, nxt;
for (var i = 0, len = format.length; i < len; ++i) {
chr = format.substr(i , 1);
if (chr != "%") {
buffer += chr;
continue;
}
nxt = format.substr(i + 1, 1);
if (nxt == "C") { // 2-digit century (eg "19" or "20")
buffer += String(Math.flo or( /* this should be one line */
this.getFullYea r() / 100)).padFront( "0", 2);
} else if (nxt == "d") { // day of month (01 to 31)
buffer += String(this.get Date()).padFron t("0", 2);
} else if (nxt == "F") { // month of year (1 to 12)
buffer += (this.getMonth( ) + 1);
} else if (nxt == "f") { // day of month (1 to 31)
buffer += this.getDate();
} else if (nxt == "H") { // 24h hours (00 - 23)
buffer += String(this.get Hours()).padFro nt("0", 2);
} else if (nxt == "M") { // minutes (00 - 59)
buffer += String(this.get Minutes()).padF ront("0", 2);
} else if (nxt == "m") { // month of year (01 to 12)
buffer += String(this.get Month() + 1).padFront("0" , 2);
} else if (nxt == "n") { // newline
buffer += "\n";
} else if (nxt == "R") { // 24h time (%H:%M)
buffer += String(this.get Hours()).padFro nt("0", 2)
+ ":"
+ String(this.get Minutes()).padF ront("0", 2);
} else if (nxt == "S") { // seconds (00 - 59)
buffer += String(this.get Seconds()).padF ront("0", 2);
} else if (nxt == "T") { // 24h time (%H:%M:%S)
buffer += String(this.get Hours()).padFro nt("0", 2)
+ ":"
+ String(this.get Minutes()).padF ront("0", 2)
+ ":"
+ String(this.get Seconds()).padF ront("0", 2);
} else if (nxt == "Y") { // 4-digit year
buffer += this.getFullYea r();
} else if (nxt == "y") { // 2-digit year
var y = String(this.get FullYear());
buffer += y.substr(y.leng th -2, 2);
} else if (nxt == "%") { // literal "%" character
buffer += "%";
} else {
buffer += format.substr(i , 2);
}
++i; // skip next
}
return buffer;
}

Date.prototype. fmt = function(format ) {
var d = this;
return format.replace(/%([CdFfHMmnRSTYy%])/g,
function(m, p1) {
switch (p1)
{
case "C": return String(Math.flo or(d.getFullYea r() / 100))
.padFront("0", 2);
case "d": return String(d.getDat e()).padFront(" 0", 2);
case "F": return d.getMonth() + 1;
case "f": return d.getDate();
case "H": return String(d.getHou rs()).padFront( "0", 2);
case "M": return String(d.getMin utes()).padFron t("0", 2);
case "m": return String(d.getMon th() + 1).padFront("0" , 2);
case "n": return "\n";
case "R": return String(d.getHou rs()).padFront( "0", 2)
+ ":"
+ String(d.getMin utes()).padFron t("0", 2);
case "S": return String(d.getSec onds()).padFron t("0", 2);
case "T": return String(d.getHou rs()).padFront( "0", 2)
+ ":"
+ String(d.getMin utes()).padFron t("0", 2)
+ ":"
+ String(d.getSec onds()).padFron t("0", 2);
case "Y": return d.getFullYear() ;
case "y": return String(d.getFul lYear() % 100).padFront(" 0", 2);
default: return p1;
}
});
};


PointedEars
--
Anyone who slaps a 'this page is best viewed with Browser X' label on
a Web page appears to be yearning for the bad old days, before the Web,
when you had very little chance of reading a document written on another
computer, another word processor, or another network. -- Tim Berners-Lee

[Dr J R Stockton]

Re: Javascript and working with dates

On Sep 19, 4:12 pm, rhaazy <rha...@gmail.c omwrote:

I need to write some javascript that will return a date string in the
form mm/dd/yyyy.

Deprecanda est FFF.

The date needs to be today's date - 30 days.

Be aware that the user's date may differ from your date.

Is there a relatively straight forward way to do this?

D = new Date() ; D.setDate(D.get Date()-30)
with (D) X = String(10100000 0 + getMonth()*1e6 + getDate()*1e4 +
getFullYear())
.replace(/(.)(\d\d)(\d\d)/, "$2/$3/")
with (D) X = String(100 + getFullYear()*1 e4 + getMonth()*1e2 +
getDate())
.replace(/(\d{4})(\d\d)(\ d\d)/, "$2/$3/$1")

Only one of the with statements is required. This gives 2 2 4 digit
fields, unlike some.

--
(c) John Stockton, near London, UK. Posting with Google.
Mail: J.R.""""""""@ph ysics.org or (better) via Home Page at
Web: <URL:http://www.merlyn.demo n.co.uk/>
FAQish topics, acronyms, links, etc.; Date, Delphi, JavaScript, ...

[Conrad Lender]

Re: Javascript and working with dates

On 2008-09-20 13:03, Thomas 'PointedEars' Lahn wrote:

Date.prototype. fmt = function(format ) {
var d = this;
return format.replace(/%([CdFfHMmnRSTYy%])/g,
function(m, p1) {
switch (p1)
{
case "C": return String(Math.flo or(d.getFullYea r() / 100))
.padFront("0", 2);
case "d": return String(d.getDat e()).padFront(" 0", 2);
case "F": return d.getMonth() + 1;
case "f": return d.getDate();
case "H": return String(d.getHou rs()).padFront( "0", 2);
case "M": return String(d.getMin utes()).padFron t("0", 2);
case "m": return String(d.getMon th() + 1).padFront("0" , 2);
case "n": return "\n";
case "R": return String(d.getHou rs()).padFront( "0", 2)
+ ":"
+ String(d.getMin utes()).padFron t("0", 2);
case "S": return String(d.getSec onds()).padFron t("0", 2);
case "T": return String(d.getHou rs()).padFront( "0", 2)
+ ":"
+ String(d.getMin utes()).padFron t("0", 2)
+ ":"
+ String(d.getSec onds()).padFron t("0", 2);
case "Y": return d.getFullYear() ;
case "y": return String(d.getFul lYear() % 100).padFront(" 0", 2);
default: return p1;
}
});
};

Nice touch, thanks.

Performance is comparable, by the way: about the same in Opera and
Firefox2; the string buffer method is about 30% faster in Firefox3, and
the regex method is about 20% faster in IE7. Outside of benchmarks, the
performance difference is negligible, of course. I think I like your
approach better, it's more compact and easier to maintain.


- Conrad

[Conrad Lender]

Re: Javascript and working with dates

On 2008-09-20 09:43, sasuke wrote:

A improvement here might be using Array as buffer instead of String

That would be implementation dependant. After a quick check it looks
like an array buffer is actually a little slower in the browsers that
I've tested. IIRC, the speed difference between string concatenation and
array joins only favors the array if the substrings are rather long.


- Conrad