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

Assuming the JS Date object standard where months are numbered from 0, and you have your daysInMonth array:

var days = daysInMonth[month] + ((month === 1) && (year % 4 === 0) && ((year % 100 !== 0) || (year % 400 === 0)));

will give you the number of days in the month, with 28 increased to 29 iff the month is February and the year is a leap year.