JQUERY:Calculate age years ,month,days

function getAge(dateString) {
    var now = new Date();
    var today = new Date(now.getYear(), now.getMonth(), now.getDate());

    var yearNow = now.getYear();
    var monthNow = now.getMonth();
    var dateNow = now.getDate();

    var dob = new Date(dateString.substring(6, 10),
                     dateString.substring(0, 2) - 1,
                     dateString.substring(3, 5)
                     );

    var yearDob = dob.getYear();
    var monthDob = dob.getMonth();
    var dateDob = dob.getDate();
    var age = {};
    var ageString = "";
    var yearString = "";
    var monthString = "";
    var dayString = "";


    yearAge = yearNow - yearDob;

    if (monthNow >= monthDob)
        var monthAge = monthNow - monthDob;
    else {
        yearAge--;
        var monthAge = 12 + monthNow - monthDob;
    }

    if (dateNow >= dateDob)
        var dateAge = dateNow - dateDob;
    else {
        monthAge--;
        var dateAge = 31 + dateNow - dateDob;

        if (monthAge < 0) {
            monthAge = 11;
            yearAge--;
        }
    }

    age = {
        years: yearAge,
        months: monthAge,
        days: dateAge
    };

    if (age.years > 1) yearString = " years";
    else yearString = " year";
    if (age.months > 1) monthString = " months";
    else monthString = " month";
    if (age.days > 1) dayString = " days";
    else dayString = " day";


    if ((age.years > 0) && (age.months > 0) && (age.days > 0))
        ageString = age.years + yearString + ", " + age.months + monthString + ", and " + age.days + dayString ;
    else if ((age.years == 0) && (age.months == 0) && (age.days > 0))
        ageString = "Only " + age.days + dayString ;
    else if ((age.years > 0) && (age.months == 0) && (age.days == 0))
        ageString = age.years + yearString;
    else if ((age.years > 0) && (age.months > 0) && (age.days == 0))
        ageString = age.years + yearString + " and " + age.months + monthString ;
    else if ((age.years == 0) && (age.months > 0) && (age.days > 0))
        ageString = age.months + monthString + " and " + age.days + dayString;
    else if ((age.years > 0) && (age.months == 0) && (age.days > 0))
        ageString = age.years + yearString + " and " + age.days + dayString;
    else if ((age.years == 0) && (age.months > 0) && (age.days == 0))
        ageString = age.months + monthString;
    else ageString = "Could not calculate age!";

    return ageString;
}