ฟังก์ชั่นหา Day of Year

function dayofyear(d) {   // d is a Date object
   var yn = d.getFullYear();
   var mn = d.getMonth();
   var dn = d.getDate();
   var d1 = new Date(yn,0,1,12,0,0); // noon on Jan. 1
   var d2 = new Date(yn,mn,dn,12,0,0); // noon on input date
   var ddiff = Math.round((d2-d1)/864e5);
   return ddiff+1;
}



ที่มา: http://www.webdeveloper.com/forum/showthread.php?125428-Does-javascript-have-a-simple-get-day-of-the-year-type-function&p=657625