JavaScript \\ 获取上周四的日期

Question

How can i Get Date of Last Thursday via JavaScript?

If Thursday is today then get -7 days.

After that format output like '17 April 2016'.

Answer 1

First it would be easier to help you by sharing your code ;)

You can get last Thursday by using the method Date.getDay() which returning the current day of the week.

Like this :

var now = new Date();
var daysAfterLastThursday = (-7 + 4) - now.getDay(); // 7 = number of days in week, 4 = the thursdayIndex (0= sunday)
var currentMs = now.getTime();
var lastThursday = new Date(currentMs + (daysAfterLastThursday * 24 * 60 * 60 * 1000));
alert("Last Thursday : " + lastThursday);

jsFiddle

Answer 2

Here's a function I wrote that works for all cases.

/**
 * @param {Date} date - the initial Date
 * @param {('Mon'|'Tue'|'Wed'|'Thurs'|'Fri'|'Sat'|'Sun')} day - the day of week
 * @returns {Date} - the Date of last occurrence or same Date if day param is invalid
 */
function getLastDayOccurence (date, day) {
  const d = new Date(date.getTime());
  const days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thurs', 'Fri', 'Sat'];
  if (days.includes(day)) {
    const modifier = (d.getDay() + days.length - days.indexOf(day)) % 7 || 7;
    d.setDate(d.getDate() - modifier);
  }
  return d;
}

If looking for the last occurrence of a Thursday from today, usage would be as follows:

const lastThursday = getLastDayOccurence(new Date(), 'Thurs');

Also answered here: https://stackoverflow.com/a/59145062/5436697

Answer 3

Simple, you can do it yourself.

1. Find current day d
2. Add d by 3
3. Mod the result of step 2 by 7 using (result % 7)
4. If result of step 3 is 0 subtract 7 from today's date, else subtract result of step 3 from today's date.

Answer 4

这可能是不好的形式，但我已经使用 PHP 的 strtotime 函数来做到这一点。

const d = "<?php echo date("d M Y", strtotime ("last thursday")); ?>";

Answer 5

var weekdays = [ "Sun", "Mon", "Tue", "Wed", "Thurs", "Fri", "Sat" ];

function getDateForLastOccurence( strDay )
{
   var date = new Date();
   var index = weekDays.indexOf(strDay);
   var difference =  date.getDay() - index; 
   if (difference < 0 ) 
   {
      difference = -7 - difference;
   }
   date.setDate( date.getDate() + difference );
   return  date;
}

getDateForLastOccurence( "Tue" );
getDateForLastOccurence( "Thurs" );