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up vote 2 down vote favorite

I found a lot of links to validate string if it is a date.

Like here and here.

But anyway I cannot figure out how to validate if we have this thing:

6/6/2012 where first 6 is month and the second 6 is days

and also if user input it like that:

06/06/2012

Any clue how it could be done in a proper way?

Thanks!!

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2 Answers

up vote 11 down vote accepted

Here, this should work with any date format with 4 digit year and any delimiter. I extracted it from my plugin Ideal Forms which validates dates and much more.

var isValidDate = function (value, userFormat) {
  var

  userFormat = userFormat || 'mm/dd/yyyy', // default format

  delimiter = /[^mdy]/.exec(userFormat)[0],
  theFormat = userFormat.split(delimiter),
  theDate = value.split(delimiter),

  isDate = function (date, format) {
    var m, d, y
    for (var i = 0, len = format.length; i < len; i++) {
      if (/m/.test(format[i])) m = date[i]
      if (/d/.test(format[i])) d = date[i]
      if (/y/.test(format[i])) y = date[i]
    }
    return (
      m > 0 && m < 13 &&
      y && y.length === 4 &&
      d > 0 && d <= (new Date(y, m, 0)).getDate()
    )
  }

  return isDate(theDate, theFormat)

}
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That's really cool. Let me test it! Thanks! –  Clark Kent Jun 27 '12 at 1:47
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up vote 4 down vote

Use a regular expression.

var dateRegEx = /^(0[1-9]|1[012]|[1-9])[- /.](0[1-9]|[12][0-9]|3[01]|[1-9])[- /.](19|20)\d\d$/

console.log("06/06/2012".match(dateRegEx) !== null) // true
console.log("6/6/2012".match(dateRegEx) !== null) // true
console.log("6/30/2012".match(dateRegEx) !== null) // true
console.log("30/06/2012".match(dateRegEx) !== null) // false

Learn about RegEx.

Edit - A Disclaimer

As @elclanrs pointed out, this only validates the string's format, and not the actual date, which means that dates like February 31st would pass. However, since the OP only asks "to validate date string format," I'll keep this answer here because for some, it might be all you need.

As a note, the jQuery Validation plugin that the OP was using, also only validates format.

Finally, for those wondering, if you needed to validate the date, and not just the format, this regular expression would have ~2% rate of failure over the domain of (1-12)/(1-31)/(1900-2099) date strings. Please don't use this in Mission Critical code for JPL.

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1  
This won't do it for every case ie. console.log("11/31/2012".match(dateRegEx)) // true –  elclanrs Jun 27 '12 at 1:55
    
@elclanrs Um...isn't that a valid (M)M/(D)D/YYYY date string? Are you saying it should return false? –  merv Jun 27 '12 at 2:00
    
Well, November doesn't have 31 days...so yeah I guess it should return false. –  elclanrs Jun 27 '12 at 2:02
    
@elclanrs - Aha! good catch...sometimes it's easy to get ahead of oneself. –  merv Jun 27 '12 at 2:04
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