This function returns age when given a DOB.

GetAge.js

//This function returns age when given a DOB. getAge(DOB)
//You can also get the age on a given date. getAge(DOB, onDate)

function getAge(d1, d2) {
    d2 = d2 || new Date();
    var diff = d2.getTime() - d1.getTime();
    return Math.floor(diff / (1000 * 60 * 60 * 24 * 365.25));
}