jquery自动去除form表单中input框前后的空格

<script type="text/javascript">
$(document).ready(function() {
     $(‘#searchform input‘).keyup(trimkeyup);
 });
 function trimkeyup(e) {
    lucene_objInput = $(this);
     if(e.keyCode != 38 && e.keyCode != 40 && e.keyCode != 13) {
       var im = $.trim(lucene_objInput.val());
       lucene_objInput.val(im); 
    }
}  
</script>