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

Issue

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?

Solution

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

Answered By – Christian C. Salvadó

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