Comparing Two Dates

[Mike N.]

I am currently using a function to validate a form on the client side
(see code below). At the end of the function, I would like it to also
compare a startDate against an endDate to ensure that the endDate is
greater than (comes after) the startDate. The date format I'm using is
MM/DD/YYYY and it's writing to an MS SQL Server 2000 database table
via ASP. THANKS!!!

function ValidateForm()
{
//validate STATUS element
if (document.form. status[0].selected)
{
alert("Please select a Status");
document.form.s tatus.focus();
return false;
}

//validate NAME element
if (document.form. name.value=="")
{
alert("Please enter a Name")
document.form.n ame.select();
return false;
}

//validate START DATE element
if ((document.form .startDate.valu e=="") ||
(document.form. startDate.value =="mm/dd/yyyy"))
{
alert("Please enter a valid Start Date")
document.form.s tartDate.focus( );
return false;
}

//validate END DATE element
if ((document.form .endDate.value= ="") ||
(document.form. endDate.value== "mm/dd/yyyy"))
{
alert("Please enter a valid End Date")
document.form.e ndDate.focus();
return false;
}

//validate DATES
//check to ensure that endDate is > startDate
}

[Thomas 'PointedEars' Lahn]

Re: Comparing Two Dates

Mike N. wrote:[color=blue]
> I am currently using a function to validate a form on the client side
> (see code below). At the end of the function, I would like it to also
> compare a startDate against an endDate to ensure that the endDate is
> greater than (comes after) the startDate. The date format I'm using is
> MM/DD/YYYY [...][/color]

The Date() constructor takes the year, month and date as arguments (in this
order, among others) and creates Date objects which have a getTime() method
to reflect the number of milliseconds that have passed for this date since
January 1, 1970 00:00:00.

RegExp.exec() used on the input string will let you extract year, month and
date from it.

This has been explained in detail several times before. RTFM, RTFFAQ.


PointedEars

[Dr John Stockton]

Re: Comparing Two Dates

JRS: In article <41070FCB.20906 06@PointedEars. de>, dated Wed, 28 Jul
2004 04:30:35, seen in news:comp.lang. javascript, Thomas 'PointedEars'
Lahn <PointedEars@nu rfuerspam.de> posted :[color=blue]
>Mike N. wrote:[color=green]
>> I am currently using a function to validate a form on the client side
>> (see code below). At the end of the function, I would like it to also
>> compare a startDate against an endDate to ensure that the endDate is
>> greater than (comes after) the startDate. The date format I'm using is
>> MM/DD/YYYY [...][/color]
>
>The Date() constructor takes the year, month and date as arguments (in this
>order, among others) and creates Date objects which have a getTime() method
>to reflect the number of milliseconds that have passed for this date since
>January 1, 1970 00:00:00.[/color]

Careless. You should be aware of the need to specify GMT or UTC here,
even though it will not affect the OP's use.
[color=blue]
>RegExp.exec( ) used on the input string will let you extract year, month and
>date from it.[/color]

True, but not necessary.

Browsers in locations where it is appropriate to specify MM/DD/YYYY will
accept an MM/DD/YYYY string into new Date() .


Dates in the ISO 8601 date field order can be compared directly, if the
separators are constants, leading zeroes are used, the range 1000-9999
is not exceeded, and four-digit years are used. That AIUI is a FIPS and
ANSI standard, BTW.

Dates in the OP's form can easily be converted to ISO, by concatenating
substrings or using a RegExp; see below, and my datefmts.htm#RU SA, and
UStoISO8601(St) in my js-date9.htm.

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