js如何获取前后连续n天的时间

 function GetDateStr(AddDayCount) {
    var dd = new Date();
    dd.setDate(dd.getDate()+AddDayCount);//获取AddDayCount天后的日期
    var y = dd.getFullYear();
    var m = (dd.getMonth()+1)<10?"0"+(dd.getMonth()+1):(dd.getMonth()+1);//获取当前月份的日期，不足10补0
    var d = dd.getDate()<10?"0"+dd.getDate():dd.getDate();//获取当前几号，不足10补0
    return y+"-"+m+"-"+d;
 }

 console.log("半年前："+GetDateStr(-180));
 console.log("三月前："+GetDateStr(-90));
 console.log("一月前："+GetDateStr(-30));
 console.log("昨天："+GetDateStr(-1));
 console.log("今天："+GetDateStr(0));
 console.log("明天："+GetDateStr(1));
 console.log("后天："+GetDateStr(2));
 console.log("一月后："+GetDateStr(30));
 console.log("三月后："+GetDateStr(90));
 console.log("半年后："+GetDateStr(180));