Question

59

JavaScript Date.getWeek()?

rated 0 times [ 62] [ 3] / answers: 1 / hits: 105856 / 13 Years ago, sat, january 28, 2012, 12:00:00

I'm looking for a tested solid solution for getting current week of the year for specified date. All I can find are the ones that doesn't take in account leap years or just plain wrong. Does anyone have this type of stuff?

Or even better a function that says how many weeks does month occupy. It is usually 5, but can be 4 (feb) or 6 (1st is sunday and month has 30-31 days in it)

=================
UPDATE:

Still not sure about getting week #, but since I figured out it won't solve my problem with calculating how many weeks month occupy, I abandoned it.

Here's a function to find out how many weeks exactly month occupy on the calendar:

getWeeksNum: function(year, month) {

    var daysNum = 32 - new Date(year, month, 32).getDate(),

        fDayO = new Date(year, month, 1).getDay(),

        fDay = fDayO ? (fDayO - 1) : 6,

        weeksNum = Math.ceil((daysNum + fDay) / 7);

    return weeksNum;

}

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gabriel

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3 Years ago

answered 13 Years ago kourtney · Accepted Answer

/**

 * Returns the week number for this date.  dowOffset is the day of week the week

 * "starts" on for your locale - it can be from 0 to 6. If dowOffset is 1 (Monday),

 * the week returned is the ISO 8601 week number.

 * @param int dowOffset

 * @return int

 */

Date.prototype.getWeek = function (dowOffset) {

/*getWeek() was developed by Nick Baicoianu at MeanFreePath: http://www.meanfreepath.com */



    dowOffset = typeof(dowOffset) == 'number' ? dowOffset : 0; //default dowOffset to zero

    var newYear = new Date(this.getFullYear(),0,1);

    var day = newYear.getDay() - dowOffset; //the day of week the year begins on

    day = (day >= 0 ? day : day + 7);

    var daynum = Math.floor((this.getTime() - newYear.getTime() - 

    (this.getTimezoneOffset()-newYear.getTimezoneOffset())*60000)/86400000) + 1;

    var weeknum;

    //if the year starts before the middle of a week

    if(day < 4) {

        weeknum = Math.floor((daynum+day-1)/7) + 1;

        if(weeknum > 52) {

            nYear = new Date(this.getFullYear() + 1,0,1);

            nday = nYear.getDay() - dowOffset;

            nday = nday >= 0 ? nday : nday + 7;

            /*if the next year starts before the middle of

              the week, it is week #1 of that year*/

            weeknum = nday < 4 ? 1 : 53;

        }

    }

    else {

        weeknum = Math.floor((daynum+day-1)/7);

    }

    return weeknum;

};

Usage:

var mydate = new Date(2011,2,3); // month number starts from 0

// or like this

var mydate = new Date('March 3, 2011');

alert(mydate.getWeek());

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