JavaScriptで年齢計算

JavaScriptで年齢計算。

■ソース
function ageCalculator(selectY, selectM, selectD) {
var dateObj = new Date();
var today = parseInt("" + dateObj.getFullYear() + zeroformat(dateObj.getMonth() + 1) + zeroformat(dateObj.getDate()));
var birthday = parseInt("" + selectY + zeroformat(selectM) + zeroformat(selectD));
var age = (today - birthday) / 10000;
return parseInt(age);
}
function zeroformat(v) {
return (String(v).length == 1) ? '0' + v : v;
}
console.log(ageCalculator (2000, 01, 01)); //13

■参考サイト
http://shanabrian.com/web/javascript/form08.php