Validate number of days in a given month

Question

Performance is of the utmost importance on this one guys... This thing needs to be lightning fast!


How would you validate the number of days in a given mont

Answer 1

I've been doing this using the Date object (assuming it's compiled, and hence blindingly fast compared to scripting).

The trick is that if you enter a too high number for the date part, the Date object wraps over into the next month. So:

var year = 2009;
var month = 1;
var date = 29;

var presumedDate = new Date(year, month, date);

if (presumedDate.getDate() != date)
    WScript.Echo("Invalid date");
else
    WScript.Echo("Valid date");

This will echo "Invalid date" because presumedDate is actually March 1st.

This leaves all the trouble of leap years etc to the Date object, where I don't have to worry about it.

Neat trick, eh? Dirty, but that's scripting for you...