butona tıklayınca textfield e veri

<input type="text" name="textfield" id="textfield">
<input type="button" name="button" id="button" value="Getir">

<input type="text" id="guvenlikkodu" />
<input type="button" onclick='ChangeCode();' name="button" id="button" value="Getir">

<script language="javascript">
			function ChangeCode(){
				document.getElementById('guvenlikkodu').value='asd';
				return false;
			}
		</script>

<script src="http://code.jquery.com/jquery-1.11.0.min.js"></script>
<script type="text/javascript">
$(function() {
    $('#button').click(function(){ // button tıklanacak button idsi
            $.get("fast.php", function( data ) { // fast.php datayi cekecegin sayfa
                $('#textfield').val(data); //textfield yazdiracagin input id si
            });
    });
});
</script>