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);

};

let dt = dob;

        let age = '';

        let bY = Number(moment(dt).format('YYYY')); 
        let bM = Number(moment(dt).format('MM')); 
        let bD = Number(moment(dt).format('DD')); 

        let tY = Number(moment().format('YYYY')); 
        let tM = Number(moment().format('MM')); 
        let tD = Number(moment().format('DD')); 


        age += (tY - bY) + ' Y ';

        if (tM < bM) {
            age += (tM - bM + 12) + ' M ';
            tY = tY - 1;
        } else {
            age += (tM - bM) + ' M '
        }

        if (tD < bD) {
            age += (tD - bD + 30) + ' D ';
            tM = tM - 1;
        } else {
            age += (tD - bD) + ' D '
        }
        
        //AGE MONTH DAYS
        console.log(age);

试试这个。

function getAge(dateString) {
    var today = new Date();
    var birthDate = new Date(dateString);
    var age = today.getFullYear() - birthDate.getFullYear();
    var m = today.getMonth() - birthDate.getMonth();
    if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) {
        age--;
    }
    return age;
}

我相信你的代码中唯一看起来粗糙的是substr部分。

小提琴:http://jsfiddle.net/codeandcloud/n33RJ/

这对我来说是最优雅的方式:

const getAge = (birthDateString) => { const today = new Date(); const birthDate = new Date(birthDateString); const yearsDifference = today.getFullYear() - birthDate.getFullYear(); 如果( 今天。getmonth () < birthDate.getMonth() || . getmonth ( (today.getMonth() === birthDate.getMonth() && today.getDate() < birthDate.getDate())) ) { 返回yearsDifference - 1; ｝ 返回yearsDifference; }; console.log (getAge (' 2018-03-12 '));

为了测试生日是否已经过去，我定义了一个帮助函数Date.prototype。getDoY，它有效地返回一年中的天数。剩下的就不言自明了。

Date.prototype.getDoY = function() {
    var onejan = new Date(this.getFullYear(), 0, 1);
    return Math.floor(((this - onejan) / 86400000) + 1);
};

function getAge(birthDate) {
    function isLeap(year) {
        return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
    }

    var now = new Date(),
        age = now.getFullYear() - birthDate.getFullYear(),
        doyNow = now.getDoY(),
        doyBirth = birthDate.getDoY();

    // normalize day-of-year in leap years
    if (isLeap(now.getFullYear()) && doyNow > 58 && doyBirth > 59)
        doyNow--;

    if (isLeap(birthDate.getFullYear()) && doyNow > 58 && doyBirth > 59)
        doyBirth--;

    if (doyNow <= doyBirth)
        age--;  // birthday not yet passed this year, so -1

    return age;
};

var myBirth = new Date(2001, 6, 4);
console.log(getAge(myBirth));

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')