这个问题已经超过10年了，没有人回答过提示，他们已经有了YYYYMMDD格式的出生日期?

如果你有一个YYYYMMDD格式的过去日期和当前日期，你可以像这样快速计算它们之间的年数:

var pastDate = '20101030';
var currentDate = '20210622';
var years = Math.floor( ( currentDate - pastDate ) * 0.0001 );
// 10 (10.9592)

你可以得到当前日期格式为YYYYMMDD，如下所示:

var now = new Date();

var currentDate = [
    now.getFullYear(),
    ('0' + (now.getMonth() + 1) ).slice(-2),
    ('0' + now.getDate() ).slice(-2),
].join('');

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

使用javascript从出生日期获取年龄(年，月和日)

函数calcularEdad(年，月和日)

function calcularEdad(fecha) {
        // Si la fecha es correcta, calculamos la edad

        if (typeof fecha != "string" && fecha && esNumero(fecha.getTime())) {
            fecha = formatDate(fecha, "yyyy-MM-dd");
        }

        var values = fecha.split("-");
        var dia = values[2];
        var mes = values[1];
        var ano = values[0];

        // cogemos los valores actuales
        var fecha_hoy = new Date();
        var ahora_ano = fecha_hoy.getYear();
        var ahora_mes = fecha_hoy.getMonth() + 1;
        var ahora_dia = fecha_hoy.getDate();

        // realizamos el calculo
        var edad = (ahora_ano + 1900) - ano;
        if (ahora_mes < mes) {
            edad--;
        }
        if ((mes == ahora_mes) && (ahora_dia < dia)) {
            edad--;
        }
        if (edad > 1900) {
            edad -= 1900;
        }

        // calculamos los meses
        var meses = 0;

        if (ahora_mes > mes && dia > ahora_dia)
            meses = ahora_mes - mes - 1;
        else if (ahora_mes > mes)
            meses = ahora_mes - mes
        if (ahora_mes < mes && dia < ahora_dia)
            meses = 12 - (mes - ahora_mes);
        else if (ahora_mes < mes)
            meses = 12 - (mes - ahora_mes + 1);
        if (ahora_mes == mes && dia > ahora_dia)
            meses = 11;

        // calculamos los dias
        var dias = 0;
        if (ahora_dia > dia)
            dias = ahora_dia - dia;
        if (ahora_dia < dia) {
            ultimoDiaMes = new Date(ahora_ano, ahora_mes - 1, 0);
            dias = ultimoDiaMes.getDate() - (dia - ahora_dia);
        }

        return edad + " años, " + meses + " meses y " + dias + " días";
    }

函数esNumero

function esNumero(strNumber) {
    if (strNumber == null) return false;
    if (strNumber == undefined) return false;
    if (typeof strNumber === "number" && !isNaN(strNumber)) return true;
    if (strNumber == "") return false;
    if (strNumber === "") return false;
    var psInt, psFloat;
    psInt = parseInt(strNumber);
    psFloat = parseFloat(strNumber);
    return !isNaN(strNumber) && !isNaN(psFloat);
}

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));

还有另一个解决方案:

/**
 * Calculate age by birth date.
 *
 * @param int birthYear Year as YYYY.
 * @param int birthMonth Month as number from 1 to 12.
 * @param int birthDay Day as number from 1 to 31.
 * @return int
 */
function getAge(birthYear, birthMonth, birthDay) {
  var today = new Date();
  var birthDate = new Date(birthYear, birthMonth-1, birthDay);
  var age = today.getFullYear() - birthDate.getFullYear();
  var m = today.getMonth() - birthDate.getMonth();
  if (m < 0 || (m === 0 && today.getDate() < birthDate.getDate())) {
    age--;
  }
  return age;
}

function age()
{
    var birthdate = $j('#birthDate').val(); // in   "mm/dd/yyyy" format
    var senddate = $j('#expireDate').val(); // in   "mm/dd/yyyy" format
    var x = birthdate.split("/");    
    var y = senddate.split("/");
    var bdays = x[1];
    var bmonths = x[0];
    var byear = x[2];
    //alert(bdays);
    var sdays = y[1];
    var smonths = y[0];
    var syear = y[2];
    //alert(sdays);

    if(sdays < bdays)
    {
        sdays = parseInt(sdays) + 30;
        smonths = parseInt(smonths) - 1;
        //alert(sdays);
        var fdays = sdays - bdays;
        //alert(fdays);
    }
    else{
        var fdays = sdays - bdays;
    }

    if(smonths < bmonths)
    {
        smonths = parseInt(smonths) + 12;
        syear = syear - 1;
        var fmonths = smonths - bmonths;
    }
    else
    {
        var fmonths = smonths - bmonths;
    }

    var fyear = syear - byear;
    document.getElementById('patientAge').value = fyear+' years '+fmonths+' months '+fdays+' days';
}