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

The days of each month are known easily by exception of February for detail of leap years:

I leave an implementation based on the algorithm that solves this problem:

Algorithm

if (year is not divisible by 4) then (it is a common year)
else if (year is not divisible by 100) then (it is a leap year)
else if (year is not divisible by 400) then (it is a common year)
else (it is a leap year)

• More info: https://en.wikipedia.org/wiki/Leap_year#Algorithm

Implementation in Javascript

/**
 * Doc: https://en.wikipedia.org/wiki/Leap_year#Algorithm
 * param : month is indexed: 1-12
 * param: year
 **/
		function daysInMonth(month, year) {
			switch (month) {
				case 2 : //Febrary
					if (year % 4) {
						return 28; //common year
					}
					if (year % 100) {
						return 29; //  leap year
					}
					
					if (year % 400) {
						return 28; //common year
					}
					return 29; //  leap year
				case 9 : case 4 : case 6 : case 11 :
					return 30;
				default :
					return 31
			}
		}
    
    /** Testing daysInMonth Function **/
    $('#month').change(function() {
        var mVal = parseInt($(this).val());
        var yVal = parseInt($('#year').val());
        $('#result').text(daysInMonth(mVal, yVal));
    });
    

Year


month


   days: