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Home > Forums > Programmers > Web Development > Javascript Forum

Working with dates and conditional text color change

thread216-1686363
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newme01 (Programmer)
20 Jun 12 18:30
Hi all,

I have two dates with format [mm/dd/yy]
and I want to get the number of days difference.

and how can I make the text of "X" days to become red if the result is negative

Im a quick learner if i just know the basics. hope you can guide me to a good start on my coding.


here where im at now:

<html>
<head>
<title></title>
</head>
<body>

<script language="javascript">
function subtractdate(form)
{
var a = form.datetextbox1.value;
var b = form.datetextbox2.value;
var datedifference = parseFloat(a) - parseFloat(b) + " days difference"; // <--i think this is not correct
document.getElementById('result').innerHTML = datedifference;
}

</script>

<form>
ie. [mm/dd/yy] - [mm/dd/yy] = X/-X days difference<br><br>

<input type=text name="datetextbox1" onchange="subtractdate(this.form);">-
<input type=text name="datetextbox2" onchange="subtractdate(this.form);">
<div id="result"></div>
</form>


</body>
</html>
feherke (Programmer)
21 Jun 12 4:33
Hi

Quote (newme01)

Im a quick learner if i just know the basics.
Then I hope this will help with the next steps :
  • Better use 'mm/dd/yyyy' date format, that will be parsed correctly by the Date constructor.
  • After instantiating the two objects just subtract them ( same result as subtracting their milliseconds since epoch value obtainable with getTime() ) and will get the difference in milliseconds.
  • Divide it to get the number of days. round() it if need whole days.

CODE --> FireBug-console

>>> new Date('06/21/12') // wrong
Date {Fri Jun 21 1912 00:00:00 GMT+0300 (BMT)}
>>> new Date('06/21/2012') // correct
Date {Thu Jun 21 2012 00:00:00 GMT+0300 (EEST)}
>>> new Date('06/21/2012')-new Date('01/01/2012')
14857200000
>>> new Date('06/21/2012').getTime()-new Date('01/01/2012').getTime()
14857200000
>>> (new Date('06/21/2012')-new Date('01/01/2012'))/(1000*60*60*24)
171.95833333333334
>>> Math.round((new Date('06/21/2012')-new Date('01/01/2012'))/(1000*60*60*24))
172

Feherke.
http://feherke.github.com/

newme01 (Programmer)
24 Jun 12 9:44

Quote (>>> new Date('06/21/12') // wrong)

Thanks for reply. thats probably why I can make my code to work.

Quote ((1000*60*60*24))

What are these represent (yr*month*days*hrs)?

-----

What if we do a reverse. like X day(s) + '06/12/2012'

how do you code it?
ChrisHirst (IS/IT--Management)
24 Jun 12 9:52

Quote:

What are these represent (yr*month*days*hrs)?

javascript time intervals are in milliseconds (1/1000 second)

so
(60 seconds per min) * (60 minutes per hour) * (24 hours per day) * 1000 = milliseconds in a day.

Chris.

Indifference will be the downfall of mankind, but who cares?
Time flies like an arrow, however, fruit flies like a banana.
Webmaster Forum

newme01 (Programmer)
24 Jun 12 10:01
Please disregard my first question. I got the answer here:

Quote (Quote ((1000*60*60*24)))

= 1000ms/sec, 60 sec/min, 60 min/hr, 24 hr/day
newme01 (Programmer)
24 Jun 12 10:03
Thanks ChrisHirst for the quick reply.


What if we do a reverse. like X day(s) + '06/12/2012'

how do you code it?
feherke (Programmer)
24 Jun 12 10:11
Hi

Quote (newme01)

What if we do a reverse. like X day(s) + '06/12/2012'

how do you code it?
Instantiate a date.
Get its numeric equivalent.
Calculate the time interval as numeric value. ( Used 15 days in the example. )
Do the math with the two numeric values.
Update the date object.

CODE --> FireBug-Console

>>> d=new Date('06/12/2012')
Date {Tue Jun 12 2012 00:00:00 GMT+0300 (EEST)}
>>> dn=d.getTime()
1339448400000
>>> tn=15*24*60*60*1000
1296000000
>>> dn+=tn
1340744400000
>>> d.setTime(dn)
1340744400000
>>> d
Date {Wed Jun 27 2012 00:00:00 GMT+0300 (EEST)}

Feherke.
http://feherke.github.com/

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