javascript 如何在Javascript中将周数转换为日期
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原文地址: http://stackoverflow.com/questions/7580824/
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How to convert a week number to a date in Javascript
提问by raimonbosch
I had tried to find some work done but I haven't had luck. Any ideas?
我曾试图找到一些已完成的工作，但我没有运气。有任何想法吗？
Examples:
例子：
Week, 1, 2001 => 2001-01-01
2001 年第 1 周 => 2001-01-01
Week, 26, 2007 => 2007-06-01
2007 年第 26 周 => 2007-06-01
回答by Julien Kronegg
As Kevin's code does not implement ISO 8601 properly (first day of the first week of year must be a Monday), I've corrected it and ended up with (also check it on jsfiddle):
由于凯文的代码没有正确实现 ISO 8601（一年第一周的第一天必须是星期一），我已经更正了它并结束了（也在jsfiddle 上检查）：
function firstDayOfWeek(week, year) {
if (year==null) {
year = (new Date()).getFullYear();
}
var date = firstWeekOfYear(year),
weekTime = weeksToMilliseconds(week),
targetTime = date.getTime() + weekTime;
return date.setTime(targetTime);
}
function weeksToMilliseconds(weeks) {
return 1000 * 60 * 60 * 24 * 7 * (weeks - 1);
}
function firstWeekOfYear(year) {
var date = new Date();
date = firstDayOfYear(date,year);
date = firstWeekday(date);
return date;
}
function firstDayOfYear(date, year) {
date.setYear(year);
date.setDate(1);
date.setMonth(0);
date.setHours(0);
date.setMinutes(0);
date.setSeconds(0);
date.setMilliseconds(0);
return date;
}
/**
* Sets the given date as the first day of week of the first week of year.
*/
function firstWeekday(firstOfJanuaryDate) {
// 0 correspond au dimanche et 6 correspond au samedi.
var FIRST_DAY_OF_WEEK = 1; // Monday, according to iso8601
var WEEK_LENGTH = 7; // 7 days per week
var day = firstOfJanuaryDate.getDay();
day = (day === 0) ? 7 : day; // make the days monday-sunday equals to 1-7 instead of 0-6
var dayOffset=-day+FIRST_DAY_OF_WEEK; // dayOffset will correct the date in order to get a Monday
if (WEEK_LENGTH-day+1<4) {
// the current week has not the minimum 4 days required by iso 8601 => add one week
dayOffset += WEEK_LENGTH;
}
return new Date(firstOfJanuaryDate.getTime()+dayOffset*24*60*60*1000);
}
function assertDateEquals(effectiveDate, expectedDate, description) {
if ((effectiveDate==null ^ expectedDate==null) || effectiveDate.getTime()!=expectedDate.getTime()) {
console.log("assert failed: "+description+"; effective="+effectiveDate+", expected="+expectedDate);
}
}
function assertEquals(effectiveValue, expectedValue, description) {
if (effectiveValue!=expectedValue) {
console.log("assert failed: "+description+"; effective="+effectiveValue+", expected="+expectedValue);
}
}
// expect the first day of year to be a monday
for (var i=1970; i<2050; i++) {
assertEquals(firstWeekOfYear(i).getDay(), 1, "first day of year "+i+" must be a monday"); // 1=Monday
}
// assert some future first day of first week of year; source: http://www.epochconverter.com/date-and-time/weeknumbers-by-year.php
assertDateEquals(firstWeekOfYear(2013), new Date(Date.parse("Dec 31, 2012")), "2013");
assertDateEquals(firstWeekOfYear(2014), new Date(Date.parse("Dec 30, 2013")), "2014");
assertDateEquals(firstWeekOfYear(2015), new Date(Date.parse("Dec 29, 2014")), "2015");
assertDateEquals(firstWeekOfYear(2016), new Date(Date.parse("Jan 4, 2016")), "2016");
assertDateEquals(firstWeekOfYear(2017), new Date(Date.parse("Jan 2, 2017")), "2017");
assertDateEquals(firstWeekOfYear(2018), new Date(Date.parse("Jan 1, 2018")), "2018");
assertDateEquals(firstWeekOfYear(2019), new Date(Date.parse("Dec 31, 2018")), "2019");
assertDateEquals(firstWeekOfYear(2020), new Date(Date.parse("Dec 30, 2019")), "2020");
assertDateEquals(firstWeekOfYear(2021), new Date(Date.parse("Jan 4, 2021")), "2021");
assertDateEquals(firstWeekOfYear(2022), new Date(Date.parse("Jan 3, 2022")), "2022");
assertDateEquals(firstWeekOfYear(2023), new Date(Date.parse("Jan 2, 2023")), "2023");
assertDateEquals(firstWeekOfYear(2024), new Date(Date.parse("Jan 1, 2024")), "2024");
assertDateEquals(firstWeekOfYear(2025), new Date(Date.parse("Dec 30, 2024")), "2025");
assertDateEquals(firstWeekOfYear(2026), new Date(Date.parse("Dec 29, 2025")), "2026");
console.log("All assertions done.");
I included test cases for some dates to check that the first day of the first week of year is a Monday and checked some dates based on http://www.epochconverter.com/date-and-time/weeknumbers-by-year.php
我包括了一些日期的测试用例，以检查一年中第一周的第一天是星期一，并根据http://www.epochconverter.com/date-and-time/weeknumbers-by-year检查了一些日期。 php
回答by Peter
Someone might be still interested in a more contained version:
有人可能仍然对包含更多内容的版本感兴趣：
function firstDayOfWeek (year, week) {
// Jan 1 of 'year'
var d = new Date(year, 0, 1),
offset = d.getTimezoneOffset();
// ISO: week 1 is the one with the year's first Thursday
// so nearest Thursday: current date + 4 - current day number
// Sunday is converted from 0 to 7
d.setDate(d.getDate() + 4 - (d.getDay() || 7));
// 7 days * (week - overlapping first week)
d.setTime(d.getTime() + 7 * 24 * 60 * 60 * 1000
* (week + (year == d.getFullYear() ? -1 : 0 )));
// daylight savings fix
d.setTime(d.getTime()
+ (d.getTimezoneOffset() - offset) * 60 * 1000);
// back to Monday (from Thursday)
d.setDate(d.getDate() - 3);
return d;
}
回答by Quantamax
I took the original idea from Kevin, with some tweaks, coz the original code is returning milliseconds. Here you go:
我从Kevin那里得到了最初的想法，做了一些调整，因为原始代码返回毫秒。干得好：
var d = firstDayOfWeek(9, 2013);
console.log(d.format("yyyy-MM-dd"));
////////////////////////////// Main Code //////////////////////////////
function firstDayOfWeek(week, year) {
if (typeof year !== 'undefined') {
year = (new Date()).getFullYear();
}
var date = firstWeekOfYear(year),
weekTime = weeksToMilliseconds(week),
targetTime = date.getTime() + weekTime - 86400000;
var result = new Date(targetTime)
return result;
}
function weeksToMilliseconds(weeks) {
return 1000 * 60 * 60 * 24 * 7 * (weeks - 1);
}
function firstWeekOfYear(year) {
var date = new Date();
date = firstDayOfYear(date,year);
date = firstWeekday(date);
return date;
}
function firstDayOfYear(date, year) {
date.setYear(year);
date.setDate(1);
date.setMonth(0);
date.setHours(0);
date.setMinutes(0);
date.setSeconds(0);
date.setMilliseconds(0);
return date;
}
function firstWeekday(date) {
var day = date.getDay(),
day = (day === 0) ? 7 : day;
if (day > 3) {
var remaining = 8 - day,
target = remaining + 1;
date.setDate(target);
}
return date;
}
回答by Kevin Smith
Take a look at this fiddle. First, it gets the first week of the specified year. This takes into account that according to ISO 8601the first week of the year is the first week containing a wednesday. Then it adds the weeks to the acquired date and returns the result.
看看这个小提琴。首先，它获取指定年份的第一周。这考虑到根据ISO 8601，一年中的第一周是包含星期三的第一周。然后它将周数添加到获取的日期并返回结果。
function firstDayOfWeek(week, year) {
var date = firstWeekOfYear(year),
weekTime = weeksToMilliseconds(week),
targetTime = weekTime + date.getTime();
return date.setTime(targetTime);
}
