// The last day of a week for 2 September 2014 11:55:00:
var result = lastDayOfWeek(new Date(2014, 8, 2, 11, 55, 0))
//=> Sat Sep 06 2014 00:00:00
// If the week starts on Monday, the last day of the week for 2 September 2014 11:55:00:
var result = lastDayOfWeek(new Date(2014, 8, 2, 11, 55, 0), { weekStartsOn: 1 })
//=> Sun Sep 07 2014 00:00:00