一周的第一天/最后一天

为了得到即将到来的一周的第一天，你可以这样使用:

函数getUpcomingSunday() { const date = new date (); const today = date.getDate(); const currentDay = date.getDay(); const newDate =日期。setDate(今天- currentDay + 7); return newDate (newDate); ｝ console.log (getUpcomingSunday ());

或者获得最晚的第一天:

函数getLastSunday() { const date = new date (); const today = date.getDate(); const currentDay = date.getDay(); const newDate =日期。setDate(今天- (currentDay || 7)); return newDate (newDate); ｝ console.log (getLastSunday ());

*根据您所在的时区，一周的开始不必从周日开始，它可以从周五、周六、周一或您的机器设置的任何其他日子开始。这些方法可以解释。

*你也可以像这样使用toISOString方法格式化它:

周一上午00点到周一上午00点返回。

const now = new Date()
const startOfWeek = new Date(now.getFullYear(), now.getMonth(), now.getDate() - now.getDay() + 1)
const endOfWeek = new Date(now.getFullYear(), now.getMonth(), startOfWeek.getDate() + 7)

接受的答案将不适用于在UTC-XX:XX时区运行代码的任何人。

这里的代码将工作，无论时区仅为日期。如果你也提供时间，这就行不通了。只提供日期或解析日期并将其作为输入。我在代码开始时提到了不同的测试用例。

function getDateForTheMonday(dateString) { var orignalDate = new Date(dateString) var modifiedDate = new Date(dateString) var day = modifiedDate.getDay() diff = modifiedDate.getDate() - day + (day == 0 ? -6:1);// adjust when day is sunday modifiedDate.setDate(diff) var diffInDate = orignalDate.getDate() - modifiedDate.getDate() if(diffInDate == 6) { diff = diff + 7 modifiedDate.setDate(diff) } console.log("Given Date : " + orignalDate.toUTCString()) console.log("Modified date for Monday : " + modifiedDate) } getDateForTheMonday("2022-08-01") // Jul month with 31 Days getDateForTheMonday("2022-07-01") // June month with 30 days getDateForTheMonday("2022-03-01") // Non leap year February getDateForTheMonday("2020-03-01") // Leap year February getDateForTheMonday("2022-01-01") // First day of the year getDateForTheMonday("2021-12-31") // Last day of the year

一个只有数学计算的例子，没有任何Date函数。

const date = new date (); Const ts = +日期; const mondayTS = ts % (60 * 60 * 24 * (7-4) * 1000); const monday =新的日期(星期一); console.log(monday.toISOString()， 'Day:'， monday.getDay());

const formatTS = v => new Date(v).toISOString(); const adjust = (v, d = 1) => v - v % (d * 1000); const d = new Date('2020-04-22T21:48:17.468Z'); const ts = +d; // 1587592097468 const test = v => console.log(formatTS(adjust(ts, v))); test(); // 2020-04-22T21:48:17.000Z test(60); // 2020-04-22T21:48:00.000Z test(60 * 60); // 2020-04-22T21:00:00.000Z test(60 * 60 * 24); // 2020-04-22T00:00:00.000Z test(60 * 60 * 24 * (7-4)); // 2020-04-20T00:00:00.000Z, monday // So, what does `(7-4)` mean? // 7 - days number in the week // 4 - shifting for the weekday number of the first second of the 1970 year, the first time stamp second. // new Date(0) ---> 1970-01-01T00:00:00.000Z // new Date(0).getDay() ---> 4

不知道它的性能如何，但这是可行的。

var today = new Date();
var day = today.getDay() || 7; // Get current day number, converting Sun. to 7
if( day !== 1 )                // Only manipulate the date if it isn't Mon.
    today.setHours(-24 * (day - 1));   // Set the hours to day number minus 1
                                         //   multiplied by negative 24
alert(today); // will be Monday

或作为一个函数:

# modifies _date_
function setToMonday( date ) {
    var day = date.getDay() || 7;  
    if( day !== 1 ) 
        date.setHours(-24 * (day - 1)); 
    return date;
}

setToMonday(new Date());

使用Date对象的getDay方法，您可以知道一周中的天数(0=星期日，1=星期一，等等)。

然后你可以用这个天数加1，例如:

function getMonday(d) {
  d = new Date(d);
  var day = d.getDay(),
      diff = d.getDate() - day + (day == 0 ? -6:1); // adjust when day is sunday
  return new Date(d.setDate(diff));
}

getMonday(new Date()); // Mon Nov 08 2010