JSFiddle - React, Tailwind, and code Playground

JavaScript

var startDate = "9-DEC-2011";
startDate = new Date(startDate.replace(/-/g, "/"));
var endDate = "", noOfDaysToAdd = 13, count = 0;
while(count < noOfDaysToAdd){
    endDate = new Date(startDate.setDate(startDate.getDate() + 1));
    if(endDate.getDay() != 0 && endDate.getDay() != 6){
       count++;
    }
}
alert(endDate);//You can format this date as per your requirement