从 JavaScript 中的周数获取不正确的日期范围

Question

我有一个 javascript 函数，它根据周数计算日期范围

Date.prototype.getWeek = function weekCalc() {
  const date = new Date(this.getTime());
  date.setHours(0, 0, 0, 0);
  date.setDate((date.getDate() + 3 - (date.getDay() + 6)) % 7);
  const week1 = new Date(date.getFullYear(), 0, 4);

  return 1 + Math.round((((date.getTime() - week1.getTime()) / 86400000 - 3 + (week1.getDay() + 6)) % 7) / 7);
};

const getDateRangeOfWeek = (weekNo, y) => {
  const d1 = new Date(`${y}`);
  const pastDays = d1.getDay() - 1;
  d1.setDate(d1.getDate() - pastDays);
  d1.setDate(d1.getDate() + 7 * (weekNo - d1.getWeek()));
  const rangeIsFrom = `${`0${d1.getDate()}`.slice(-2)}/${`0${d1.getMonth() + 1}`.slice(-2)}/${d1.getFullYear().toString().substring(2)}`;
  d1.setDate(d1.getDate() + 6);
  const rangeIsTo = `${`0${d1.getDate()}`.slice(-2)}/${`0${d1.getMonth() + 1}`.slice(-2)}/${d1.getFullYear().toString().substring(2)}`;
  return `${rangeIsFrom}-${rangeIsTo}`;
};

console.log(getDateRangeOfWeek(52, 2016));

当您根据 ISO 8061 在 2016 年第 52 周对其进行测试时，它会给出

getDateRangeOfWeek(52, 2016);
"19/12/16-25/12/16"

这有点不正确，请查看https://www.calendar-week.org/2016/52

我不确定上面的实现出了什么问题？

Answer 1

我没有费心挖掘您的代码，但我确实拼凑了一个可以检索所需结果的解决方案：

function addDays(date, days) {
  let newDate = new Date(date);
  newDate.setDate(newDate.getDate() + days)
  return newDate;
}

let locale = new Intl.DateTimeFormat('en-GB',{ dateStyle: 'short'});

function formatDate(date) {
  return locale.format(date)
}

function getDateOfISOWeek(w, y) {
  let simple = new Date(y, 0, 1 + (w - 1) * 7);
  let dow = simple.getDay();
  let ISOweekStart = simple;
  if (dow <= 4)
      ISOweekStart.setDate(simple.getDate() - simple.getDay() + 1);
  else
      ISOweekStart.setDate(simple.getDate() + 8 - simple.getDay());
  let ISOweekEnd = addDays(ISOweekStart, 6);

  //let dateSpanLong = `${ISOweekStart} to ${ISOweekEnd}`; // date objects to do with what you please;
  let dateSpanShort = `${formatDate(ISOweekStart)} to ${formatDate(ISOweekEnd)}`;
  return dateSpanShort;
}

console.log(getDateOfISOWeek(52,2016)) // returns '26/12/2016 to 01/01/2017'

这是Intl.DateTimeFormat options 的一个很好的参考...

我从 adding the 6 days 借来的另一个 StackOverflow 帖子...

我用它来获取correct start of the week