jquery select 移动option 转

<html> 
<head> 
<script type='text/javascript'    
src='http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.js'></script> 
<script type='text/javascript'> 
$(function() {   
    $("#btnMoveUp,#btnMoveDown").click(function() {   
        var $opt = $("#selList option:selected:first");   
        if (!$opt.length) return;   
        if (this.id == "btnMoveUp") 
            $opt.prev().before($opt);   
        else 
            $opt.next().after($opt);   
        });   
        //按Alt加上下鍵也可以移動   
        $("#selList").keydown(function(evt) {   
                if (!evt.altKey) return;   
                var k = evt.which;
                if (k == 38) { $("#btnMoveUp").click(); return false; }   
                else 
                    if (k == 40) { $("#btnMoveDown").click(); return false; }   
        });
});   
</script> 
</head><body> 
<select id='selList' size='7' style='width: 100px'> 
<option>Item 1</option> 
<option>Item 2</option> 
<option>Item 3</option> 
<option>Item 4</option> 
<option>Item 5</option> 
</select><br /> 
<input type="button" value="▲"  /> 
<input type="button" value="▼" /> 
</body> 
</html>