输入天数自动算出时间是多少

GetDateTime(dayNum) {
    var dateDay = new Date();
    dateDay .setDate(dateDay .getDate() + dayNum)
    console.log(dateDay );
    var y = dateDay .getFullYear();
    var m = (dateDay .getMonth() + 1) < 10 ? "0" + (dateDay .getMonth() + 1) : (dateDay .getMonth() + 1); 
    var d = dateDay .getDate() < 10 ? "0" + dateDay .getDate() : dateDay .getDate();
    return y + "-" + m + "-" + d;
   },

使用：

 this.GetDateTime(30)