JavaScript: Return date, if valid.

ba-dateifvalid.js

function dateIfValid(y, m, d) {
  var date = new Date(y, --m, d);
  return !isNaN(+date) && date.getFullYear() == y && date.getMonth() == m && date.getDate() == d && date;
}

ba-dateifvalid.min.js

function dateIfValid(y,m,d){var _=new Date(y,--m,d);return!isNaN(+_)&&_.getFullYear()==y&&_.getMonth()==m&&_.getDate()==d&&_}

In a tweet as well.

date.getTime() could be +date if you wanted to. Also, @Kambfhase pointed out you could use --m to crunch some more bytes.

function isDateValid(y, m, d) {
  var date = new Date(y, --m, d);
  return !isNaN(+date) && date.getFullYear() == y && date.getMonth() == m && date.getDate() == d;
}

Since I needed the created date object, I wrote it like this:

function get_valid_date(year, month, day){
  var y = parseInt( year, 10 );
  var m = parseInt( month, 10 );
  var d = parseInt( day, 10 );
  var date = new Date( y, m - 1, d );
  if ( !isNaN(date.getTime()) && date.getFullYear() == y &&
       date.getMonth() == m - 1 && date.getDate() == d ) {
    return date;
  } else {
    return;
  }
}

Ok, so I changed it to dateIfValid which now returns a date object, if the date is valid. Even more useful, and still tweetable!

I know the regexp could be mucked with, but you could do smth like below to reduce the day + year check.

function dateIfValid(y, m, d) {
  var date = new Date(y, --m, d);
  return (/(\d+) .*?(\d{4})/.exec(date)||'').slice(1) == d+','+y && date.getMonth() == m && date;
}

golf'ed to

function dateIfValid(y,m,d,_){
  return(/(\d+) .*?(\d{4})/.exec(_=new Date(y,--m,d))||'').slice(1)==d+','+y&&_.getMonth()==m&&_
}