[removed] calculate number of days in month for a given year

Question

I have a HTML page with 3 dropdowns for the month, day and year and I was wondering if there was a way to populate the month drop down properly depending on the month and ye

Answer 1

Date.prototype.daysinMonth= function(){
var d= new Date(this.getFullYear(), this.getMonth()+1, 0);
return d.getDate();
};

function daysinMonthfromInput  (month, year) {
     return (new Date(year, month - 1, 1)).daysinMonth();
};
function fillallday (elem, month, year) {
     var options = null;
     var elementExists = document.getElementById(elem);

     if (elementExists != null) {

         this.removeOptions(elementExists);
         var opt = document.createElement('option');
         opt.value = "";
         opt.innerHTML = "---Day---";
         elementExists.appendChild(opt);
         if (month != "") {
             if (typeof (year) === "undefined") {
                 year = new Date().getFullYear();
             }
             if (year == "") {
                 year = new Date().getFullYear();
             }
             var days = daysinMonthfromInput(month, year);
             for (var i = 1; i <= days; i++) {
                 var opt = document.createElement('option');
                 opt.value = i;
                 opt.innerHTML = i;
                 elementExists.appendChild(opt);
             }
         }
     }

 }