JavaScript regular expression to match mm/dd/yyyy format - restrict to numeric input only

Question

I'm trying to write some regular expressions to validate MM/DD/YYYY date entry. Each part of the date is a separate input textfield separated by a "/" like:

01 / 16 / 1985

For a date of January 16, 1985.

I have it now where it only allows numeric entries, which was easy using replace() and a simple regex. BTW, regex's are not my forte, I don't do much of them, maybe once or twice every couple years.

Below is the code I'm using as well as some psuedo-regex underneath my replace(). I'm having a hard time tying the numeric entry regex in with the date formatting regex I'm trying to achieve (commented out under replace())

//MM  
$(this).keyup(function() {  
    //allow only numbers  
    this.value = this.value.replace(/[^0-9]/g, '');  

    //(0[1-9]|1[012])  
    //matching 01 (Jan) to 09 (Sep) to 10 (Oct) to 12 (Dec)  
});

//DD  
$(this).keyup(function() {
    //allow only numbers
    this.value = this.value.replace(/[^0-9]/g, '');

    //(0[1-9]|[12][0-9]|3[01])
    //matching 01-09, 10-19, 20-29, 30-31
    //(not worried about picking 31 in February)
});

//YYYY  
$(this).keyup(function() {
    //allow only numbers
    this.value = this.value.replace(/[^0-9]/g, '');

    //(\d{4})
    //really simple 4 digit, but don't really want 1245 as a valid year

    //a range from 1900-current year would be great
//( 1900-newDate().getFullYear() )
    //something like this possible?
);

Answer 1

(?:0[1-9]|1[0-2])/(?:0[1-9]|[12][0-9]|3[01])/(?:19|20)[0-9]{2}

• Matches 01 to 12 / 01 to 31 / 1900 to 2099
• Limitation: 31st of feb (and the likes) matches
• (?:text) prevents the backreference, remove the ?: if you would need it
• Depending on how you use it, you may have to escape the / --> \\/

Three different fields is just a matter of splitting up, the / being the delimiter.

• Day (01 to 31)

   0[1-9]|[12][0-9]|3[01] 

• Month (01 to 12)

   0[1-9]|1[0-2] 

• Year (1900-2099)

   (?:19|20)[0-9]{2} 

Answer 2

You'd better do a split on / and test all individual parts. But if you really want to use a regex you can try this one :

#^(?:(?:(?:(?:0?[13578])|(1[02]))/31/(19|20)?\d\d)|(?:(?:(?:0?[13-9])|(?:1[0-2]))/(?:29|30)/(?:19|20)?\d\d)|(?:0?2/29/(?:19|20)(?:(?:[02468][048])|(?:[13579][26])))|(?:(?:(?:0?[1-9])|(?:1[0-2]))/(?:(?:0?[1-9])|(?:1\d)|(?:2[0-8]))/(?:19|20)?\d\d))$#

Explanation:

^            # start of line
 (?:         # group without capture
             # that match 31st of month 1,3,5,7,8,10,12
   (?:       # group without capture
     (?:     # group without capture
       (?:   # group without capture
         0?  # number 0 optionnal
         [13578] # one digit either 1,3,5,7 or 8
       )     # end group
       |     # alternative
       (1[02]) # 1 followed by 0,1 or 2
     )       # end group
     /       # dash
     31      # number 31
     /       # dash
     (19|20)? #numbers 19 or 20 optionnal
     \d\d    # 2 digits from 00 to 99 
   )         # end group
|
   (?:(?:(?:0?[13-9])|(?:1[0-2]))/(?:29|30)/(?:19|20)?\d\d)
|
   (?:0?2/29/(?:19|20)(?:(?:[02468][048])|(?:[13579][26])))
|
   (?:(?:(?:0?[1-9])|(?:1[0-2]))/(?:(?:0?[1-9])|(?:1\d)|(?:2[0-8]))/(?:19|20)?\d\d)
 )
$

I've explained the first part, leaving the rest as an exercise.

This match one invalid date : 02/29/1900 but is correct for any other dates between 01/01/1900 and 12/31/2099

Answer 3

the regular expression for the date format that you want should be something like this

[0-9]{2}/[0-9]{2}/[0-9]{4}

this should work.