我对之前的答案做了一些更新。

var calculateAge = function(dob) {
    var days = function(date) {
            return 31*date.getMonth() + date.getDate();
        },
        d = new Date(dob*1000),
        now = new Date();

    return now.getFullYear() - d.getFullYear() - ( measureDays(now) < measureDays(d));
}

我希望这对你有所帮助

我使用这种方法使用逻辑而不是数学。 它既精确又快速。 参数是这个人生日的年、月和日。 它以整数形式返回这个人的年龄。

function calculateAge(year, month, day) {
        var currentDate = new Date();
        var currentYear = currentDate.getFullYear();
        var currentMonth = currentDate.getUTCMonth() + 1;
        var currentDay = currentDate.getUTCDate();
        // You need to treat the cases where the year, month or day hasn't arrived yet.
        var age = currentYear - year;
        if (currentMonth > month) {
            return age;
        } else {
            if (currentDay >= day) {
                return age;
            } else {
                age--;
                return age;
            }
        }
    }

使用ES6的干净的一行程序解决方案:

const getAge = birthDate => Math.floor((new Date() - new Date(birthDate).getTime()) / 3.15576e+10)

// today is 2018-06-13
getAge('1994-06-14') // 23
getAge('1994-06-13') // 24

我使用的是365.25天的一年(因为闰年是0.25天)，分别是3.15576e+10毫秒(365.25 * 24 * 60 * 60 * 1000)。

它有几个小时的剩余时间，所以根据用例，它可能不是最佳选择。

以下是计算年龄的简单方法:

//dob date dd/mm/yy 
var d = 01/01/1990


//today
//date today string format 
var today = new Date(); // i.e wed 04 may 2016 15:12:09 GMT
//todays year
var todayYear = today.getFullYear();
// today month
var todayMonth = today.getMonth();
//today date
var todayDate = today.getDate();

//dob
//dob parsed as date format   
var dob = new Date(d);
// dob year
var dobYear = dob.getFullYear();
// dob month
var dobMonth = dob.getMonth();
//dob date
var dobDate = dob.getDate();

var yearsDiff = todayYear - dobYear ;
var age;

if ( todayMonth < dobMonth ) 
 { 
  age = yearsDiff - 1; 
 }
else if ( todayMonth > dobMonth ) 
 {
  age = yearsDiff ; 
 }

else //if today month = dob month
 { if ( todayDate < dobDate ) 
  {
   age = yearsDiff - 1;
  }
    else 
    {
     age = yearsDiff;
    }
 }

function getAge(dateString) {

    var dates = dateString.split("-");
    var d = new Date();

    var userday = dates[0];
    var usermonth = dates[1];
    var useryear = dates[2];

    var curday = d.getDate();
    var curmonth = d.getMonth()+1;
    var curyear = d.getFullYear();

    var age = curyear - useryear;

    if((curmonth < usermonth) || ( (curmonth == usermonth) && curday < userday   )){

        age--;

    }

    return age;
}

获取欧洲日期输入时的年龄:

getAge('16-03-1989')

function change(){
    setTimeout(function(){
        var dateObj  =      new Date();
                    var month    =      dateObj.getUTCMonth() + 1; //months from 1-12
                    var day      =      dateObj.getUTCDate();
                    var year     =      dateObj.getUTCFullYear();  
                    var newdate  =      year + "/" + month + "/" + day;
                    var entered_birthdate        =   document.getElementById('birth_dates').value;
                    var birthdate                =   new Date(entered_birthdate);
                    var birth_year               =   birthdate.getUTCFullYear();
                    var birth_month              =   birthdate.getUTCMonth() + 1;
                    var birth_date               =   birthdate.getUTCDate();
                    var age_year                =    (year-birth_year);
                    var age_month               =    (month-birth_month);
                    var age_date                =    ((day-birth_date) < 0)?(31+(day-birth_date)):(day-birth_date);
                    var test                    =    (birth_year>year)?true:((age_year===0)?((month<birth_month)?true:((month===birth_month)?(day < birth_date):false)):false) ;
                   if (test === true || (document.getElementById("birth_dates").value=== "")){
                        document.getElementById("ages").innerHTML = "";
                    }                    else{
                        var age                     =    (age_year > 1)?age_year:(   ((age_year=== 1 )&&(age_month >= 0))?age_year:((age_month < 0)?(age_month+12):((age_month > 1)?age_month:      (  ((age_month===1) && (day>birth_date) ) ? age_month:age_date)          )    )); 
                        var ages                    =    ((age===age_date)&&(age!==age_month)&&(age!==age_year))?(age_date+"days"):((((age===age_month+12)||(age===age_month)&&(age!==age_year))?(age+"months"):age_year+"years"));
                        document.getElementById("ages").innerHTML = ages;
                  }
                }, 30);

};