How can convert jquery code to prototype code?

Question

I have a jquery code but is not working and seems that I need prototype code.

Here is the code: http://jsfiddle.net/qKG5F/1627/

<script type="text/javascript">
(function() {
$('form > input').keyup(function() {

    var empty = false;
    $('form > input').each(function() {
        if ($(this).val() == '') {
            empty = true;
        }
    });

    if (empty) {
        $('#search').attr('disabled', 'disabled');
    } else {
        $('#search').removeAttr('disabled');
    }
});
})()
</script>
<form>
FROM<br />
<input type="text"/><br />
TO<br />
<input type="text"/><br />     
<input type="submit" id="search" value="GO" disabled="disabled" />
</form> 

Please somebody can help me to convert this jquery to prototype code?

All kind of help will be accepted.

Answer 1

For sake of completeness I went ahead and converted your code to PrototypeJS. I optimized the code a bit (sorry can't help it) to exit when the first empty field is found.

<script type="text/javascript">
document.observe('dom:loaded',function(){
    $$('form > input').invoke('observe','keyup',function() {
        var empty = false;
        $$('form > input').each(function() {
            if (this.value == '') {
                empty = true;
                throw $break;
            }
        });
        $('search').writeAttribute('disabled',empty);
    });
});
</script>
<form>
FROM<br />
<input type="text"/><br />
TO<br />
<input type="text"/><br />     
<input type="submit" id="search" value="GO" disabled="disabled" />
</form>