实现方法如下：

/*** @param strBirthday：指的是出生日期，格式为"1990-01-01"*/function GetAge(strBirthday){           var returnAge,        strBirthdayArr=strBirthday.split("-"),        birthYear = strBirthdayArr[0],        birthMonth = strBirthdayArr[1],        birthDay = strBirthdayArr[2],          d = new Date(),        nowYear = d.getFullYear(),        nowMonth = d.getMonth() + 1,        nowDay = d.getDate();       if(nowYear == birthYear){        returnAge = 0;//同年 则为0周岁    }    else{        var ageDiff = nowYear - birthYear ; //年之差        if(ageDiff > 0){            if(nowMonth == birthMonth) {                var dayDiff = nowDay - birthDay;//日之差                if(dayDiff < 0) {                    returnAge = ageDiff - 1;                }else {                    returnAge = ageDiff;                }            }else {                var monthDiff = nowMonth - birthMonth;//月之差                if(monthDiff < 0) {                    returnAge = ageDiff - 1;                }                else {                    returnAge = ageDiff ;                }            }        }else {            returnAge = -1;//返回-1 表示出生日期输入错误 晚于今天        }    }     return returnAge;//返回周岁年龄}