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Get friday with week and year number in javascript

I have the week number and year, you need to find out the date (Friday) of this week and year.

function getFriday(week_num, year)
{
    ?

    return friday_date_object;
}

How to do it?

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4 answers

Week No. 1 - week from the first Thursday.

Here is the function to get any day:

var w2date = function(year, wn, dayNb){
    var j10 = new Date( year,0,10,12,0,0),
        j4 = new Date( year,0,4,12,0,0),
        mon1 = j4.getTime() - j10.getDay() * 86400000;
    return new Date(mon1 + ((wn - 1)  * 7  + dayNb) * 86400000);
};
console.log(w2date(2010, 1, 4));

the number of weeks starts from 1 to 52 or 53, it depends on the year.
For day numbers, 0 is Monday, 1 is Tuesday, ... and 4 is Friday.

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Use the date.js library . This is great for all date related functions.

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var DAY = 86400000;

function getFriday(weekNum, year) {
  var year = new Date(year.toString()); // toString first so it parses correctly year numbers
  var daysToFriday = (5 - year.getDay()); // Note that this can be also negative
  var fridayOfFirstWeek = new Date(year.getTime() + daysToFriday * DAY);
  var nthFriday = new Date(fridayOfFirstWeek.getTime() + (7 * (weekNum - 1) * DAY));
  return nthFriday;
}

.

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+1

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. months = new Array (31,28,31,...) if (year% 4 == 0), 29 .

days = num_week * 7;

[]. .

: year- (current + 1) -days

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0

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