关于前端:js-根据n年第n周获取此周的开始和结束日期

//格式化日期：yyyy-MM-ddfunction formatDate(date) {    var myyear = date.getFullYear();    var mymonth = date.getMonth() + 1;    var myweekday = date.getDate();    if (mymonth < 10) {        mymonth = "0" + mymonth;    }    if (myweekday < 10) {        myweekday = "0" + myweekday;    }    return (myyear + "-" + mymonth + "-" + myweekday);}//function getXDate(year, weeks, weekDay) {    weekDay %= 7;    var date = new Date(year, "0", "1");    var time = date.getTime();    weekDay == 0 ? time += weeks * 7 * 24 * 3600000 : time += (weeks - 1) * 7 * 24 * 3600000;//这里须要留神，当初这种模式是以周日为一周的完结，如果设定周日为一周的开始，去掉这个判断，抉择后者。    date.setTime(time);    return getNextDate(date, weekDay);}function getNextDate(nowDate, weekDay) {    var day = nowDate.getDay();    var time = nowDate.getTime();    var sub = weekDay - day;    time += sub * 24 * 3600000;    nowDate.setTime(time);    return nowDate;}//留神，其中的参数：第一个为年，第二个为第几周，第三个为周数，0为周日，1为周一；alert("1983第1周的星期1是:" + formatDate(getXDate(1983, 1, 1)));alert("1983第1周的星期日是:" + formatDate(getXDate(1983, 1, 0)));