Calculate an expected delivery date (accounting for holidays) in business days using JavaScript?

Question

After revisiting this script, and some modifications, the following is available to allow a user to add a feature that calculates the expected delivery date.

Answer 1

ship.setDate( safety );  // add a number of days

Doesn't add days. It sets the day. More info

The setDate() method sets the day of the Date object relative to the beginning of the currently set month.

If you want to add days do something like this:

ship.setDate(ship.getDate()+1);