Question

I have some code for validating date below:

 function validateForm() { var errFound = 0;        //var patt_date = new RegExp('^((((19|20)(([02468][048])|([13579][26]))-02-29))|((20[0-9][0-9])|(19[0-9][0-9]))-((((0[1-9])|(1[0-2]))-((0[1-9])|(1\d)|(2[0-8])))|((((0[13578])|(1[02]))-31)|(((0[1,3-9])|(1[0-2]))-(29|30)))))$'); var patt_date = new RegExp('^[0-9]{4}-(((0[13578]|(10|12))-(0[1-9]|[1-2][0-9]|3[0-1]))|(02-(0[1-9]|[1-2][0-9]))|((0[469]|11)-(0[1-9]|[1-2][0-9]|30)))$'); if (patt_date.test(document.getElementById('datefrom').value) == false){errFound = errFound + 1;document.getElementById('datefrom').className = 'error';}  if (errFound > 0)     alert('Please correct red colored field!'); else     return true; return false;    } 

Above code should work with YYYY-MM-DD format, but fail to validate date such as ‘2009-02-29’

The commented code should work (//var patt_date = new RegExp…), it can catch ‘2009-02-29’,
but it ruin the validation when i put invalid data and try to correct it, it keeps complain there something wrong with form value after i had correct them (especially on form with multiple input)

Maybe someone can fix the current regex?

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Edited, what i want just a simple replacement for above regexp, mean a new regexp pattern not the whole new method to validate date
And for reference, i simply grab the regexp pattern from:
http://www.regexlib.com/REDetails.aspx?regexp_id=694 and
http://www.regexlib.com/REDetails.aspx?regexp_id=933

Tested with 2009-02-29, 1st link work & 2nd not. Again the problem was only the 2nd regexp didn’t detect value 2009-02-29 as invalid while 1st can (but it ruin my code? so it’s must be there something wrong with it).

Thanks,
Dels

Answer 1

Don’t do the whole date validation with a regular expression, that’s really pushing the limits of what regexps were designed for. I would suggest this procedure instead:

1. Check date against regexp /^\d{4}-\d{2}-\d{2}$/
2. Extract year, month, and day using substr() and convert to integers
3. Use some if statements to validate the integers. Like so:

     if (month == 2) {         if (day == 29) {             if (year % 4 != 0 || year % 100 == 0 && year % 400 != 0) {                 // fail             }         }         else if (day > 28) {             // fail         }     }     else if (month == 4 || month == 6 || month  == 9 || month == 11) {         if (day > 30) {             // fail         }     }     else {         if (day > 31) {             // fail     } 

(That could certainly be written more concisely) Alternatively, you could probably perform this validation using Javascript’s Date class – you might have to do something like parsing the date, converting it back to a string, and checking if the two strings are equal. (I’m not a Javascript expert)