js按周数和年份获取每周的第一天

Question

你能否告诉我每周第一天获得第一周的最佳方式是什么？

我使用answer

中的代码

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

你能知道如何解决它吗？

感谢。

Answer 1

您需要偏移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));