给定日期，获得是当年的第几周

function getTodayWeekNo(){/*//将当前年的第一天默认为第一周的第一天    var today = new Date();    var beginDay = new Date(today.getFullYear(),0,1);    var weekNo = parseInt((today.getTime() - beginDay.getTime())/(7*24*60*60*1000))    return weekNo+1 ;    */            //周日为一周的第一天，周六为一周的最后一天    var todayDate = new Date();   //今天    var beginDate = new Date(todayDate.getFullYear(), 0, 1);  //今年第一天    var n = beginDate.getDay();   //今年第一天星期几    var dayCount = Math.ceil((todayDate - beginDate)/(24*60*60*1000));//今年第几天    if(n != 0){    var m = parseInt("0654321".charAt(n));    weekNo = Math.ceil((dayCount-m)/7) + 1;    }else{    weekNo = Math.ceil(dayCount/7);    }    return weekNo;}