如何设置出生日期下拉菜单中的开始年份

Question

I have some code the show the date of birth values. I would like to add one more function to this java script but unsure the best way.

The age is set on the year 2000 as default and the user can't go any lower as you have to be 13 or above to join the site.

Can I adjust this code to make the default change automatically each year?

For example next year the person can be born in 2001 to be 13, so the default would be "2001" the year after 2002 etc.

can anyone help me to automate this code instead of having to manually change it?

Please see Fiddle

var ysel = document.getElementsByName("year")[0],
    msel = document.getElementsByName("month")[0],
    dsel = document.getElementsByName("day")[0];
for (var i = 2000; i >= 1950; i--) {
    var opt = new Option();
    opt.value = opt.text = i;
    ysel.add(opt);
}
ysel.addEventListener("change", validate_date);
msel.addEventListener("change", validate_date);

function validate_date() {
    var y = +ysel.value, m = msel.value, d = dsel.value;
    if (m === "2")
        var mlength = 28 + (!(y & 3) && ((y % 100) !== 0 || !(y & 15)));
    else var mlength = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31][m - 1];
    dsel.length = 0;
    for (var i = 1; i <= mlength; i++) {
        var opt = new Option();
        opt.value = opt.text = i;
        if (i == d) opt.selected = true;
        dsel.add(opt);
    }
}
validate_date();

Answer 1

Use Date obj to find current year and subtract your preferred age

var currentYear = new Date().getFullYear();
for (var i = currentYear-13; i >= 1950; i--) {
    var opt = new Option();
    opt.value = opt.text = i;
    ysel.add(opt);
}