Presenting calculated age in textbox

Question

I've calculated the age using setFullYear and getFullYear, as I only want to use the birth year to calculate age for fun, but it doesn't work

Here's the code I've tried so far, which I think should work. Please give me some pointers:

function Onclick() 
{
     var Text1 = $("#Text1").val();

     var datetoday = new Date();
     var today = datetoday.getFullYear();
     var datebirthday = new Date();
     datebirthday.setFullYear(Text1);
     var birthday = datebirthday.getFullYear();
     var age = today - birthday;

     $("#txtAge").text(age);
 }

Answer 1

It was a simple mistake as I assumed, as it is a textbox and not a div, I should use .val instead of .text or html or innerHTML, like this:

function Onclick() {
var Text1 = $("#Text1").val();
var datetoday = new Date();
var today = datetoday.getFullYear();
var datebirthday = new Date();
datebirthday.setFullYear(Text1);
var birthday = datebirthday.getFullYear();
var age = today - birthday;
$("#txtAge").val(age);

}