我有一个漂亮的答案，虽然它不是我的代码。不幸的是，我忘记了原来的帖子。

function calculateAge(y, m, d) {
    var _birth = parseInt("" + y + affixZero(m) + affixZero(d));
    var  today = new Date();
    var _today = parseInt("" + today.getFullYear() + affixZero(today.getMonth() + 1) + affixZero(today.getDate()));
    return parseInt((_today - _birth) / 10000);
}
function affixZero(int) {
    if (int < 10) int = "0" + int;
    return "" + int;
}
var age = calculateAge(1980, 4, 22);
alert(age);

使用momentjs "fromNow"方法， 这允许您使用格式化的日期，例如:03/15/1968

var dob = document.getElementByID（“dob”）; var age = moment（dob.value）.fromNow（true）.replace（“ years”， “”）;

//fromNow(true) =>后缀“ago”不显示 //但是我们还是要去掉“years”;

作为原型版本

String.prototype.getAge = function() {
return moment(this.valueOf()).fromNow(true).replace(" years", "");

}

我检查了之前展示的例子，它们并不是在所有情况下都有效，因此我自己写了一个脚本。我测试过了，效果很好。

function getAge(birth) {
   var today = new Date();
   var curr_date = today.getDate();
   var curr_month = today.getMonth() + 1;
   var curr_year = today.getFullYear();

   var pieces = birth.split('/');
   var birth_date = pieces[0];
   var birth_month = pieces[1];
   var birth_year = pieces[2];

   if (curr_month == birth_month && curr_date >= birth_date) return parseInt(curr_year-birth_year);
   if (curr_month == birth_month && curr_date < birth_date) return parseInt(curr_year-birth_year-1);
   if (curr_month > birth_month) return parseInt(curr_year-birth_year);
   if (curr_month < birth_month) return parseInt(curr_year-birth_year-1);
}

var age = getAge('18/01/2011');
alert(age);

下面是我能想到的最简单、最准确的解决方案:

Date.prototype.getAge = function (date) {
    if (!date) date = new Date();
    return ~~((date.getFullYear() + date.getMonth() / 100
    + date.getDate() / 10000) - (this.getFullYear() + 
    this.getMonth() / 100 + this.getDate() / 10000));
}

下面是一个考虑每年2月29日至2月28日的例子。

Date.prototype.getAge = function (date) {
    if (!date) date = new Date();
    var feb = (date.getMonth() == 1 || this.getMonth() == 1);
    return ~~((date.getFullYear() + date.getMonth() / 100 + 
        (feb && date.getDate() == 29 ? 28 : date.getDate())
        / 10000) - (this.getFullYear() + this.getMonth() / 100 + 
        (feb && this.getDate() == 29 ? 28 : this.getDate()) 
        / 10000));
}

它甚至适用于负年龄!

这是我修改的尝试(用一个字符串传递给函数而不是一个日期对象):

function calculateAge(dobString) {
    var dob = new Date(dobString);
    var currentDate = new Date();
    var currentYear = currentDate.getFullYear();
    var birthdayThisYear = new Date(currentYear, dob.getMonth(), dob.getDate());
    var age = currentYear - dob.getFullYear();

    if(birthdayThisYear > currentDate) {
        age--;
    }

    return age;
}

和用法:

console.log(calculateAge('1980-01-01'));

我认为可以简单地像这样:

function age(dateString){
    let birth = new Date(dateString);
    let now = new Date();
    let beforeBirth = ((() => {birth.setDate(now.getDate());birth.setMonth(now.getMonth()); return birth.getTime()})() < birth.getTime()) ? 0 : 1;
    return now.getFullYear() - birth.getFullYear() - beforeBirth;
}

age('09/20/1981');
//35

也适用于时间戳

age(403501000000)
//34