JavaScript - get the first day of the week from current date

Question

I need the fastest way to get the first day of the week  For example  today is the 11th of November  and a Thursday  and I want the first day of this week  which is the 8th of November  and a Monday  I need the fastest method for MongoDB map function  any ideas

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Check out Date js  Date today   previous   monday

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setDate   has issues with month boundaries that are noted in comments above  A clean workaround is to find the date difference using epoch timestamps rather than the  surprisingly counterintuitive  methods on the Date object  I e   function getPreviousMonday fromDate        var dayMillisecs   24   60   60   1000          Get Date object truncated to date      var d   new Date new Date fromDate    Date    toISOString   slice 0  10            If today is Sunday  day 0  subtract an extra 7 days      var dayDiff   d getDay       0   7   0          Get date diff in millisecs to avoid setDate   bugs with month boundaries      var mondayMillisecs   d getTime   -  d getDay     dayDiff    dayMillisecs          Return date as YYYY-MM-DD string      return new Date mondayMillisecs  toISOString   slice 0  10

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I m using this  function get next week start        var now   new Date       var next week start   new Date now getFullYear    now getMonth    now getDate    8 - now getDay         return next week start

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a more generalized version of this    this will give you any day in the current week based on what day you specify   x000D   x000D    returns the relative day in the week 0   Sunday  1   Monday     6   Saturday function getRelativeDayInWeek d dy      d   new Date d     var day   d getDay          diff   d getDate   - day    day    0   -6 dy      adjust when day is sunday   return new Date d setDate diff       var monday   getRelativeDayInWeek new Date   1   var friday   getRelativeDayInWeek new Date   5    console log monday   console log friday   x000D   x000D   x000D

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Good evening   I prefer to just have a simple extension method   Date prototype startOfWeek   function  pStartOfWeek        var mDifference   this getDay   - pStartOfWeek       if  mDifference  lt  0            mDifference    7             return new Date this addDays mDifference   -1        You ll notice this actually utilizes another extension method that I use   Date prototype addDays   function  pDays        var mDate   new Date this valueOf         mDate setDate mDate getDate     pDays       return mDate       Now  if your weeks start on Sunday  pass in a  0  for the pStartOfWeek parameter  like so    var mThisSunday   new Date   startOfWeek 0    Similarly  if your weeks start on Monday  pass in a  1  for the pStartOfWeek parameter   var mThisMonday   new Date   startOfWeek 1    Regards

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This function uses the current millisecond time to subtract the current week  and then subtracts one more week if the current date is on a monday  javascript counts from sunday    function getMonday fromDate           length of one day i milliseconds   var dayLength   24   60   60   1000        Get the current date  without time      var currentDate   new Date fromDate getFullYear    fromDate getMonth    fromDate getDate           Get the current date s millisecond for this week   var currentWeekDayMillisecond     currentDate getDay      dayLength         subtract the current date with the current date s millisecond for this week   var monday   new Date currentDate getTime   - currentWeekDayMillisecond   dayLength      if  monday  gt  currentDate           It is sunday  so we need to go back further     monday   new Date monday getTime   -  dayLength   7           return monday      I have tested it when week spans over from one month to another  and also years   and it seems to work properly

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Using the getDay method of Date objects  you can know the number of day of the week  being 0 Sunday  1 Monday  etc    You can then subtract that number of days plus one  for example   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

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Here is my solution   function getWeekDates        var day milliseconds   24 60 60 1000      var dates           var current date   new Date        var monday   new Date current date getTime  - current date getDay  -1  day milliseconds       var sunday   new Date monday getTime   6 day milliseconds       dates push monday       for var i   1  i  lt  6  i             dates push new Date monday getTime   i day milliseconds              dates push sunday       return dates      Now you can pick date by returned array index

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var dt   new Date       current date of week var currentWeekDay   dt getDay    var lessDays   currentWeekDay    0   6   currentWeekDay - 1  var wkStart   new Date new Date dt  setDate dt getDate   - lessDays    var wkEnd   new Date new Date wkStart  setDate wkStart getDate     6      This will work well

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First Day of The Week  To get the date of the first day of the week from today  you can use something like so    x000D   x000D  function getUpcomingSunday     x000D    const date   new Date    x000D    const today   date getDate    x000D    const dayOfTheWeek   date getDay    x000D    const newDate   date setDate today - dayOfTheWeek   7   x000D    return new Date newDate   x000D    x000D   x000D  console log getUpcomingSunday     x000D   x000D   x000D    Or to get the last day of the week from today    x000D   x000D  function getLastSunday     x000D    const date   new Date    x000D    const today   date getDate    x000D    const dayOfTheWeek   date getDay    x000D    const newDate   date setDate today -  dayOfTheWeek    7    x000D    return new Date newDate   x000D    x000D   x000D  console log getLastSunday     x000D   x000D   x000D      Depending on your time zone  the beginning of the week doesn t has to start on Sunday  it can start on Friday  Saturday  Monday or any other day your machine is set to  Those methods will account for that     You can also format it using toISOString method like so  getLastSunday   toISOString

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Check out  moment js  Example   moment   day -7      last Sunday  0 - 7  moment   day 7      next Sunday  0   7  moment   day 10      next Wednesday  3   7  moment   day 24      3 Wednesdays from now  3   7   7   7    Bonus  works with node js too

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An example of the mathematically only calculation  without any Date functions    x000D   x000D  const date   new Date    x000D  const ts    date  x000D   x000D  const mondayTS   ts - ts    60   60   24    7-4    1000   x000D   x000D  const monday   new Date mondayTS   x000D  console log monday toISOString     Day    monday getDay     x000D   x000D   x000D     x000D   x000D  const formatTS   v   gt  new Date v  toISOString    x000D  const adjust    v  d   1    gt  v - v    d   1000   x000D   x000D  const d   new Date  2020-04-22T21 48 17 468Z    x000D  const ts    d     1587592097468 x000D   x000D  const test   v   gt  console log formatTS adjust ts  v     x000D   x000D  test                           2020-04-22T21 48 17 000Z x000D  test 60                        2020-04-22T21 48 00 000Z x000D  test 60   60                   2020-04-22T21 00 00 000Z x000D  test 60   60   24              2020-04-22T00 00 00 000Z x000D  test 60   60   24    7-4       2020-04-20T00 00 00 000Z  monday x000D   x000D     So  what does   7-4   mean  x000D     7 - days number in the week x000D     4 - shifting for the weekday number of the first second of the 1970 year  the first time stamp second  x000D         new Date 0           --- gt  1970-01-01T00 00 00 000Z x000D         new Date 0  getDay   --- gt  4 x000D   x000D   x000D

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Not sure how it compares for performance  but this works   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   Or as a function     modifies  date  function setToMonday  date         var day   date getDay      7        if  day     1            date setHours -24    day - 1         return date     setToMonday new Date

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CMS s answer is correct but assumes that Monday is the first day of the week  Chandler Zwolle s answer is correct but fiddles with the Date prototype  Other answers that play with hour minutes seconds milliseconds are wrong   The function below is correct and takes a date as first parameter and the desired first day of the week as second parameter  0 for Sunday  1 for Monday  etc    Note  the hour  minutes and seconds are set to 0 to have the beginning of the day    x000D   x000D  function firstDayOfWeek dateObject  firstDayOfWeekIndex    x000D   x000D      const dayOfWeek   dateObject getDay    x000D          firstDayOfWeek   new Date dateObject   x000D          diff   dayOfWeek  gt   firstDayOfWeekIndex   x000D              dayOfWeek - firstDayOfWeekIndex   x000D              6 - dayOfWeek x000D   x000D      firstDayOfWeek setDate dateObject getDate   - diff  x000D      firstDayOfWeek setHours 0 0 0 0  x000D   x000D      return firstDayOfWeek x000D    x000D   x000D     August 18th was a Saturday x000D  let lastMonday   firstDayOfWeek new Date  August 18  2018 03 24 00    1  x000D   x000D     outputs something like  Mon Aug 13 2018 00 00 00 GMT 0200  x000D      may vary according to your time zone  x000D  document write lastMonday  x000D   x000D   x000D

[javascript] JavaScript - get the first day of the week from current date

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