JavaScript计算日期加上指定天数后的日期

JavaScript计算日期加上指定天数后的日期转自：http://blog.chinaunix.net/uid/257761.html

//判断年份是否是闰年
function isLeapYear(year){
    
    if(year%400==0){
        return false;    
    }else if(year%4==0){
        return true;
    }else{
        return false;
    }
}
//计算日期加上天数后的日期
function addDays(date1,days){
    var monthDays=[0,3,0,1,0,1,0,0,1,0,0,1];
    var regexp=/^(\d{1,4})[-|\.]{1}(\d{1,2})[-|\.]{1}(\d{1,2})$/;
    regexp.test(date1);
    var date1Year=RegExp.$1;
    var date1Month=RegExp.$2;
    var date1Day=RegExp.$3;
    firstDate=new Date(date1Year,date1Month,date1Day);
    firstDate.setTime(firstDate.getTime()+days*1000*3600*24);
    var diff=0;
    for(j=date1Year;j<=firstDate.getYear();j++){
        if(isLeapYear(j)){
            monthDays[1]=2;
        }else{
            monthDays[1]=3;
        }
        for(i=date1Month-1;i<firstDate.getMonth()-1;i++){
            diff=diff+monthDays[i];
        }
    }
    result=firstDate.getYear()+"-"+firstDate.getMonth()+"-"+firstDate.getDate();
    if(diff!=0){
        result=addDays(result,diff);
    }
    return result;
    
}