获取本年度第几周

// 获取本年度第几周
var getYearWeek = function(a, b, c) 
{   
        var date1 = new Date(a, parseInt(b) - 1, c),
              date2 = new Date(a, 0, 1),
              d = Math.round((date1.valueOf() - date2.valueOf()) / 86400000);
        return Math.ceil((d + ((date2.getDay() + 1) - 1)) / 7);
};

getYearWeek(2019,08,15)

function getYearWeek (a,b, c) {
　　var data1 = new Date(a,b-1,c);
　　var data2 = new Date(a,0,1)
　　var value = (+data1 - (+data2)) / (24*60*60*1000)
　　return Math.ceil((value+data2.getDay())/7)
}
getYearWeek(2019,9,19)