身份证判断生日，生日判断年龄

function jsGetAge(strBirthday) {
    var returnAge;
    var strBirthdayArr = strBirthday.split("-");
    var birthYear = strBirthdayArr[0];
    var birthMonth = strBirthdayArr[1];
    var birthDay = strBirthdayArr[2];

    d = new Date();
    var nowYear = d.getFullYear();
    var nowMonth = d.getMonth() + 1;
    var nowDay = d.getDate();

    if (nowYear == birthYear) {
        returnAge = 0;
    }
    else {
        var ageDiff = nowYear - birthYear;
        if (ageDiff > 0) {
            if (nowMonth == birthMonth) {
                var dayDiff = nowDay - birthDay;
                if (dayDiff < 0) {
                    returnAge = ageDiff - 1;
                }
                else {
                    returnAge = ageDiff;
                }
            }
            else {
                var monthDiff = nowMonth - birthMonth;
                if (monthDiff < 0) {
                    returnAge = ageDiff - 1;
                }
                else {
                    returnAge = ageDiff;
                }
            }
        }
        else {
            returnAge = -1;
        }
    }

    return returnAge;
}


function GetBirthday(a) {
    if (18 == a.length) {
        var left = a.length - 12;
        var right = a.length - 4;
        var b = a.slice(left, right);
        if (8 == b.length) {
            return b.replace(/(.{4})(.{2})/, "$1-$2-");;
        }
    }
    if (15 == a.length) {
        var b = "19" + a.substr(6, 6);
        if (8 == b.length) {
            return b.replace(/(.{4})(.{2})/, "$1-$2-");;
        }
    }
    return "";
}