getting no. weeks given an year in javascript

Question

this is th javscript code i have used to get calculate the week no. from the given date....but the output i am getting is incorrect

   var dayNr   = (this.getDay() + 6) % 7;  

    target.setDate(target.getDate() - dayNr + 3);  


    var firstThursday = target.valueOf();  

    target.setMonth(0, 1);  

    if (target.getDay() != 4) {  
    target.setMonth(0, 1 + ((4 - target.getDay()) + 7) % 7);  
    }  

    return 1 + Math.ceil((firstThursday - target) / 604800000);

i want to calculate the week no. from the given date.....any other solution is also welcome...need it urgently

@WimOmbelets - the question that you referenced to shows 31st Dec 2013 as 53rd week. But actually its 1st week. Can you please explain? — Praful Bagai
– Praful Bagai, Commented Oct 28, 2013 at 9:11

Community · Accepted Answer · 2017-05-23 12:05:15Z

0

function getWeekNumber(d) {
    // Copy date so don't modify original
   var d = new Date(d);
    d.setHours(0,0,0);
    // Set to nearest Thursday: current date + 4 - current day number
    // Make Sunday's day number 7
    d.setDate(d.getDate() + 4 - (d.getDay()||7));
    // Get first day of year
    var yearStart = new Date(d.getFullYear(),0,1);
    // Calculate full weeks to nearest Thursday
    var weekNo = Math.ceil(( ( (d - yearStart) / 86400000) + 1)/7)
    // Return array of year and week number
    return [d.getFullYear(), weekNo];
}

Refrence Answer

edited May 23, 2017 at 12:05

CommunityBot

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answered Oct 28, 2013 at 8:40

Vinay Pratap Singh Bhadauria

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2 Comments

amit_183 Over a year ago

can u tell what is d?

Vinay Pratap Singh Bhadauria Over a year ago

@amit_183 d is the date

Tony Dinh · Accepted Answer · 2013-10-28 08:42:05Z

0

This code seem to work:

Date.prototype.getWeek = function() {
    var onejan = new Date(this.getFullYear(),0,1);
    return Math.ceil((((this - onejan) / 86400000) + onejan.getDay()+1)/7);
}

Taken from here: http://javascript.about.com/library/blweekyear.htm

answered Oct 28, 2013 at 8:42

Tony Dinh

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