js计算某个时间是当年的多少周

userRegist_hg.getYearWeek = function(d){
//var d = new Date(this.getFullYear(), this.getMonth(), this.getDate(), 0, 0, 0);
var DoW = d.getDay();
d.setDate(d.getDate() - (DoW + 6) % 7 + 3); // Nearest Thu
var ms = d.valueOf(); // GMT
d.setMonth(0);
d.setDate(4); // Thu in Week 1
return Math.round((ms - d.valueOf()) / (7 * 864e5)) + 1;
}

d指代传过来的Date类型的变量，返回周数！