Calculate age

calc_age.js

function calcAge(birth_date) {
        var today = new Date;

        var age = {
            years: 0,
            months: 0
        };

        age.years = today.getFullYear() - birth_date.getFullYear();

        if (today.getMonth() < birth_date.getMonth() || today.getMonth() == birth_date.getMonth() && today.getDate() < birth_date.getDate()) {
            age.years--;
        }

        age.months = today.getMonth() - birth_date.getMonth();

        if(today.getDate() < birth_date.getDate()) {
            age.months--;
        }

        if(age.months < 0) {
            age.months += 12;
        }

        if(age.years < 0 || age.months < 0) return null;

        return age;
    }