Prototype set selected option based on other select

how can I "copy" the selected option between two s that have the same options using prototype ? I tried getting the selected option from the "master" combo using

function getSelectedArea() {
  $$('#areacont1 option').find(function(ele){return !!ele.selected})
}

which returns null

And setting the second combo using

var c2ROptions = $$('select#areacont2 option')
c2ROptions[getSelectedArea()].selected = true

That obviously doesn't work because the function returns null.

Any hin开发者_JAVA技巧ts?

Thanks.

---

$('option1').observe('change', function() {
    $('option2').value = $F('option1');
});

What this code does is observe dropdown1 (that's the id of the dropdown) and when its value changes dropdown2 is update to reflect the same value.