Regular expression in Javascript to test for various dates

Question

I need a regular expression in javascript that can test for dates with the following formats:

yyyy-MM-dd (Example: 2014-12-31)
dd.MM.yyyy (Example: 31.12.2014)
dd.MM.yy (Example: 31.12.14)
ddMMyyyy (Example: 12312014)
ddMMyy (Example: 123114)
dd.M.yy (Example: 12.6.14)
dd.M.yyyy (Example: 12.6.2014)

Sorry, but I am really terrible at regular expressions. This is probably a breeze for a pro. Thanks a milion.

One of these is not like the others... Namely, the first one is in a completely different format to the others, making a single regex difficult to use. — Niet the Dark Absol
– Niet the Dark Absol, Commented Jun 11, 2014 at 15:09
You cannot (and shouldn't) use regular expressions to validate dates. Is 99.33.8888 a valid date? — georg
– georg, Commented Jun 11, 2014 at 15:14
The last two examples don't match their signature. (they are MMddyyyy) — user887675
– user887675, Commented Jun 11, 2014 at 15:22
ddMMyyyy (Example: 12312014) is incorrect: '31' is the day, and '12' is the month, so it should be MMddyyyy or the example should be rewritten. ddMMyy (Example: 123114) is incorrect: same reason. And if you're consistent with your "Example" formatting, '12' is always representing the MONTH, not the DAY, and either 31 or 6 should be the DAY. Could you modify the post to reflect the correct format (or the correct Example)? — OnlineCop
– OnlineCop, Commented Jun 11, 2014 at 16:10

Niet the Dark Absol · Accepted Answer · 2014-06-11 15:57:13Z

1

Your first pattern is too different from the others to be meaningfully merged. So: \d{4}-\d\d-\d\d

For the others, you are allowing an optional . as a separator, and either two- or four-digit years. So you have: \d\d(\.?)\d\d?\1\d\d(?:\d\d)?

The \1 in the above is to basically repeat the (\.?)'s result - ie. a dot if there was a dot before, or nothing if not.

Result:

/^(?:\d{4}-\d\d-\d\d|\d\d(\.?)\d\d?\1\d\d(?:\d\d)?)$/

edited Jun 11, 2014 at 15:57

answered Jun 11, 2014 at 15:11

Niet the Dark Absol

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8 Comments

Johann Over a year ago

So are you saying that your result can only be used for the last 4 examples but not for the first one? I thought regular expressions allowed some kind of ORing.

Niet the Dark Absol Over a year ago

@AndroidDev I broke the problem into two problems, then joined them together with the | - it is there ;)

Niet the Dark Absol Over a year ago

@AndroidDev Forgot to make the last two digits optional so it wasn't accepting two-digit years. Try now.

Johann Over a year ago

I added two more examples at the end. Would you be so kind as to include those as well :-)

Niet the Dark Absol Over a year ago

Now supports single-digit months.

|

Community · Accepted Answer · 2017-05-23 11:57:15Z

1

Have you looked here? You don't want to use regex for stuff like this, since aforementioned 99.33.8888 isn't a date.

This clever function could solve your problem:

var isDate_ = function(input) {
    var status = false;
    if (!input || input.length <= 0) {
      status = false;
    } else {
      var result = new Date(input);
      if (result == 'Invalid Date') {
        status = false;
      } else {
        status = true;
      }
    }
    return status;
  }

Edit: I forgot you need to find something to validate. You could just run a simple regex like this: [0-9-/\.]{6,10}, which matches all of your examples

edited May 23, 2017 at 11:57

CommunityBot

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answered Jun 11, 2014 at 15:21

LukasFT

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2 Comments

Johann Over a year ago

The solution MUST allow for the formatting I specified.

LukasFT Over a year ago

just remember to validate the regex in some ways.

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