JSFiddle - React, Tailwind, and code Playground

JavaScript

function pad(number, length) {
       
        var str = '' + number;
        while (str.length < length) {
            str = '0' + str;
        }
       
        return str;
    
    }

var inputString = "08-09-2017";
var dString = inputString.split('-');

var dt = new Date(dString[2],dString[1]-1,dString[0]);
dt.setDate(dt.getDate()+10);

var finalDate = pad(dt.getDate(),2) + "-" + pad(dt.getMonth()+1,2) + "-" + dt.getFullYear();
alert(finalDate);