js按周数和年份获取一周的第一天

Question

您能否告诉我，按周数和年份获取星期几的最佳方法是什么？

我从答案中使用此代码

function getDateOfWeek(week, y) {
   var d = new Date("Jan 01, "+y+" 01:00:00");
   var w = d.getTime() + 604800000 * (week-1);
   var n1 = new Date(w);
   var n2 = new Date(w + 518400000);
   return {
            dateFrom:n1,
            dateTo: n2
    }
}

getDateOfWeek（1,2017）返回日期：01.01.2017，08.01.2017

但需要：02.01.2017，08.01.2017

getDateOfWeek（53,2016）返回日期：30.12.2016，05.01.2017

但需要：26.12.2016，01.01.2017

你能知道如何解决吗？

谢谢。

Answer 1

您需要抵消day of the week

function getDateOfWeek(week, y) {
  var d = new Date("Jan 01, " + y + " 01:00:00");
  var dayMs = (24 * 60 * 60 * 1000);
  var offSetTimeStart = dayMs * (d.getDay() - 1);
  var w = d.getTime() + 604800000 * (week - 1) - offSetTimeStart; //reducing the offset here
  var n1 = new Date(w);
  var n2 = new Date(w + 518400000);
  return {
    dateFrom: n1,
    dateTo: n2
  }
}
console.log(getDateOfWeek(1, 2017));
console.log(getDateOfWeek(53, 2016));