calculateEndDate script for Airtable scripting block

calculateEndDate.js

/*******************************************************************************
Title: calculateEndDate - helper function for Airtable scripting block
Author: Kuovonne Vorderbruggen
Date Created: March 26, 2020
Copyright (c) 2020 by Kuovonne Vorderbruggen
License: MIT License

** Descripton **
This function calculates an end date based on a start date and a duration in days,
not counting weekends as part of the duration.

For example if the start date is a Friday and the duration is 2 days, the end
date would be a Tuesday. If the start date is a Monday and the duration is 5 days,
the end date would be the following Monday.

** Parameters **
startDate: a JavaScript date object (should be a Monday-Friday)
duration: integer (non-negative), duration in days to add
padDurationForWeekends: (optional) boolean, default is true
*******************************************************************************
*/
function calculateEndDate(startDate, duration, padDurationForWeekends = true) {
  let endDate = new Date(startDate.toISOString());
  endDate.setDate(endDate.getDate() + duration);
  if (! padDurationForWeekends) {
    return endDate;
  }
  let startDayOfWeek = startDate.getDay(); // should be 1-5 for Monday-Friday
  let completeWeeksInDuration = Math.floor(duration/5); // 5 days in work week
  let remainderDaysInDuration = duration % 5; // partial weeks
  // calculate if partial weeks require weekend days
  let finalWeekendDays = (startDayOfWeek + remainderDaysInDuration >= 6) ? 2 : 0;
  let weekendDays = (completeWeeksInDuration * 2) + finalWeekendDays;
  endDate.setDate(endDate.getDate() + weekendDays);
  return endDate;
}