Problems using javascript regex to validate date

Question

I'm trying to use javascript regex to validate a date input, but it is returning valid dates as invalid. I'm not an expert on regex so I don't know what is wrong with it:

/^([0-9]d{2})+(\.|-|\/)+([0-9]d{2})+(\.|-|\/)+([0-9]d{4})+$/

I want these date formats to be accepted:

23/04/2001

23-04-2001

23.04.2001

Originally I had this, but it was accepting dates with other characters on the end like 23/04/2001jhsdgf:

/\d{2}(\.|-|\/)\d{2}(\.|-|\/)\d{4}/;

A simple regex check isn't enough. `00-00-0000` matches your regex. — Salman A, Feb 04 '13 at 17:12
That is very true, how do you suggest I make sure its an actual date? 99/99/9999 would also match. — Adam, Feb 04 '13 at 17:44
I've added my answer. The date looks like UK date, you might want to omit `/` from the separator list. — Salman A, Feb 04 '13 at 19:31

score 4 · Accepted Answer · answered Feb 04 '13 at 17:06

4

Take your original regex and just add the ^ and $ from your new one to it. Problem solved.

EDIT: Although, really, the (\.|-|\/) is a mess and should be [.\/-] instead.

EDIT 2: That said, if you make the first one ([.\/-]) then you can replace the second one with \1 and then it would require both separators to be the same.

answered Feb 04 '13 at 17:06

Niet the Dark Absol

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Okay, won't my original regex allow letters as well? How do I specify numeric only and have it work properly? – Adam Feb 04 '13 at 17:08
`\d` means "any digit". It only allows numbers. – Niet the Dark Absol Feb 04 '13 at 17:09

Salman A · Answer 2 · 2013-02-04T19:29:56.357

You can check if a date is syntactically correct using a regex such as this one:

/^(\d{1,2})([-\.\/])(\d{1,2})\2(\d{4})$/

^ and $ match beginning and end of string respectively
\d{1,2} matches 1 or 2 digits
\d{4} matches exactly 4 digits
\2 matches the string captured in second capturing group (- . /)

If matched, you can use the matched date, month and year to build a new date and compare the resulting date, month, year with the matched values. Here is a function which does just that:

function checkDate(dateText) {
    var match = dateText.match(/^(\d{1,2})([-\.\/])(\d{1,2})\2(\d{4})$/);
    // "31.04.2012" -> ["31.04.2012", "31", ".", "04", "2012"]
    if (match === null) {
        return false;
    }
    var date = new Date(+match[4], +match[3] - 1, +match[1]);
    return date.getFullYear() == +match[4] && 
      date.getMonth() == +match[3] - 1 && 
      date.getDate() == +match[1];
}
checkDate("30.04.2013"); // true
checkDate("31-04-2013"); // false (April has 30 days)

+ is used to convert string to number (+"01" becomes 1)
Months are 0 based (0 = January, 1 = February, ...)
The above example assumes that the date is in dd-mm-yyyy format

The Date object attempts to correct invalid dates. Attempting to create a date such as 31-4-2013 yields 1-05-2013, the above function compares the resulting date with input parameters to check the validity.

Thanks, that has helped my understand things a whole lot better! For user friendliness and less need to validate, I have decided to use a JQuery UI datepicker and disable keypresses on that input. Seems to work a treat. Thanks for the help though, I appreciate it. — Adam, Feb 04 '13 at 20:20
For validate: mm/dd/yyyy
function checkDate(dateText) { var match = dateText.match(/^(\d{1,2})([\/])(\d{1,2})\2(\d{4})$/); if (match === null) { return false; } var date = new Date(+match[4], +match[1] - 1, +match[3]); return date.getFullYear() === +match[4] && date.getMonth() === +match[1] - 1 && date.getDate() === +match[3]; } — M.M.H.Masud, Mar 15 '16 at 14:40

Problems using javascript regex to validate date

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