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javascriptdate
Justine
Justine

Reputation: 1908

Get date given year, week number, day number within week with JavaScript

as the topic suggest - I'm looking to get a date when all I have is year (ex. 2014), week number (ex. 47) and day number within that week (ex. 3 - which would be Wednesday).

I've seen some similar questions the other way around, but reverse-engineering answers didn't provide any successful results.

Any ideas?

Upvotes: 0

Views: 278

Answers (3)

F3L1X79
F3L1X79

Reputation: 2665

From : Getting first date in week given a year,weeknumber and day number in javascript

The answer to OP would be (if dayNumber starts from 1 (Monday) - to 7 (Sunday)):

function getWeekDate(year, weekNumber, dayNumber) {
  var date = new Date(year, 0, 10, 0, 0, 0),
      day = new Date(year, 0, 4, 0, 0, 0),
      month = day.getTime() - date.getDay() * 86400000;
  return new Date(month + ((weekNumber - 1) * 7 + (dayNumber - 1)) * 86400000);
};

alert(getWeekDate(2014, 47, 3));

Upvotes: 0

esswilly
esswilly

Reputation: 239

function getDatebyWeek(year, week, day) {

  var d = {
    year: year,
    month: 0,
    day: 1
  };

  var date = new Date(d.year, d.month, d.day);
  var weekCount = 0;
  var month = 1;

  var done = false;

  while (weekCount < week) {

    while (date.getMonth() < month) {

      if (d.day % 7 === 0) {
        weekCount++;
      }

      d.day++;
      date.setDate(d.day);

      if (weekCount === week) {
        done = true;
        break;
      }

    }

    if (done) {
      break;
    }

    month++;

    d.month = month - 1;
    d.day = 1;

    date.setMonth(d.month);
    date.setDate(d.day);

  }

  if (day <= d.day && day >= (d.day - 7)) {
    return new Date(d.year, d.month - 1, day);
  } else {
    throw new Error('The day you entered is not in week ' + week);
  }

}

var wk = getDatebyWeek(2014, 47, 22);

document.write(wk.toString());

I wrote this really ugly function in case you have something against moment.js :)

Upvotes: 0

Cl&#233;ment Pr&#233;vost
Cl&#233;ment Pr&#233;vost

Reputation: 8590

I would highly recommend you to use the moment.js library. This is a complete date manipulation library.

Your problem would be solved by this moment().year(2014).week(47).day(3).toDate();

Upvotes: 4

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