Question

How to get the number of the day from the beginning of the year to a given date in JavaScript

Answer 1

function isLeapYear(year) {
  return (year % 4 === 0) && ((year % 100 !== 0) || (year % 400 === 0));
}

function getDayOfYear(year, month, day) {
  // cumulative days at the end of each month (non-leap year)
  const days = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];

  if (isLeapYear(year) && month > 2) {
    return days[month - 1] + day + 1;
  }
  return days[month - 1] + day;
}


const dayOfYear = getDayOfYear(2023, 5, 15);
console.log(dayOfYear); 



/*
run:

135

*/

 

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