How to increase the number of days in a Js date string

 

function dateAddDays(dataStr, dayCount) {
    var strdate = dataStr; // date string  
    var isdate = new Date(strdate.replace(/-/g, "/")); //Convert date string to date format  
    isdate = new Date((isdate / 1000 + (86400 * dayCount)) * 1000); //Add 1 day to the date  
    var pdate = isdate.getFullYear() + "-" + (isdate.getMonth() + 1) + "-" + (isdate.getDate()); //Convert date format to string  

    return pdate;
}