JavaScript - Validate Date

Question

I have an HTML text field. I want to validate via JavaScript that the value entered is a valid date in the form of "MM/DD/YY" or "MM/D/YY" or "MM/DD/YYYY" or "MM/D/YYYY". Is there a function that does this?

I sort of assumed there was something like isNaN but I don't see anything. Is it true that JavaScript can't validate dates?

Answer 1

You could use javascript's own Date object to check the date. Since the date object allows some mucking around with the month and day values (for example March 32 would be corrected to April 1), you can just check that the date you create matches the one you put in. You could shorten this if you want, but it's longer for clarity.

function checkDate(m,d,y)
{
   try { 

      // create the date object with the values sent in (month is zero based)
      var dt = new Date(y,m-1,d,0,0,0,0);

      // get the month, day, and year from the object we just created 
      var mon = dt.getMonth() + 1;
      var day = dt.getDate();
      var yr  = dt.getYear() + 1900;

      // if they match then the date is valid
      if ( mon == m && yr == y && day == d )
         return true; 
      else
         return false;
   }
   catch(e) {
      return false;
   }
}

Answer 2

Is it true that JavaScript can't validate dates?

No.

Is there a function that does this?

No.

You will need to write your own validation function to parse the date format (regex comes to mind) and then determine if it is valid within your specific criteria.