Zytrax this is an excellent source for regex knowledge, I use it regularly.
The following JavaScript function takes in a string and checks it against the following pattern ##/##/####. you may notice it doesn't make sure that the month is between 1-12 or the day is less then 31, it just makes sure that you entered 3 numbers and that they're separated by forward-slashes.
function validdateDate(dateString)
{
var datePattern = /^\d{2}[/]\d{2}[/]\d{4}$/;
return datePattern.test(dateString);
}
Now Validate, well that's a bit more tricky. First lets talk about what I mean by validate, if you run the date 02/29/2011 against a simple date Regex it will come back as valid, but it's clearly not since that date never occurred.
At first I thought I could just load the individual month day year into a constructor for a JavaScript Date object and just get an invalid date exception, but no such luck, lovely JavaScript will just bump the date up to 03/01/2011. Good bad it doesn't really matter, what matters is that I still haven't validated my Date. It's high school programming time.
To resolve this issue first we need a function to check if we're dealing with a leap year, simple enough you can grab the algorithm from numerous sites; I got this one from Wikipedia or if your super lazy it's below.
function isLeapYear(year)
{
if(year%400==0)
return true;
else if(year%100==0)
return false;
else if(year%4==0)
return true;
return false;
}
Now that we can tell if we're dealing with a leap year lets check to make sure that our date is an actual date. that has occurred.
function verifyDate(dateString)
{
var daysInMonth = [31,28,31,30,31,30,31,31,30,31,30,31];
if(dateString.length != 10)
return false;
var da = dateString.split("/");
if(da[2] <= new Date().getFullYear())
{
if(da[0] > 0 && da[0] < 13)
{
if(da[0] == 2 && isLeapYear(da[2]))
return (da[1] > 0 && da[1] < 30);
else
return (da[1] > 0 && da[1] < daysInMonth[da[0]-1]);
}
}
return false;
}
Well there you have it, are there other much more robust ways to check date, sure there are, could I have written this function to take in some sort of pattern to check against rather then just month/day/year, absolutely, but i'm not writing an API, I'm just making a one off function to filter out shitty data before it hits my server.
